Should I consider a high mileage ( nearly 160 000 miles ) TD6 vogue in outstanding condition and full dealer service history . Registered November 2004 . 3 owners
It is a long way from me and seller does not know if the transmission is original . Can the GM gearbox last that long or should it likely have a replacement .
I am curious to know the service life of parts such as turbo , alternator , water pump , air conditioning compressor , injectors , transfer case , diffs .

Gearbox is definitely questionable at that mileage, so I'd get proof it's been repaired/replaced. Got - 2017 SDV8 Autobiography in Loire Blue
Had- 2008 TDV8 Vogue SE in Java black
Had - 2007 S/C in Stornoway Grey

Air bags, shocks, suspension bushes, subframe bushes, steering rack, wheel bearings, drive shafts, propshafts are some other items to think about...

Any early, highish mileage FF will require money spending on it if you want it to drive like a new car..

Look at my build thread, there is a list of the stuff I have changed on mine in the first year of ownership, mine is now driving beautifully and goes better than it ever has done but if I had had to pay someone else to do all these items it would have cost a small fortune... mine has done 145,000 miles now...

You can't buy any 10year+ sophisticated vehicle and not expect to spend a significant amount of money to keep it in tip top condition, it just doesn't work... If you just want it to scratch an itch and you will dump it at the first sign of big bills then go for it... if not be prepared to spend some money and be rewarded with one of the best vehicles ever made (not the best made vehicle though)

Good luck Pete

__________________________________________________
2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Parchment over Navy Interior. Sold
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand, Jet Interior. Sold
2002 L322 Vogue 4.4 V8 Epson Green, Ivory over Aspen Interior (Fatty Offroader) Sold
-Click for Project Fatty off roader-

Brake pipes will also need checking, especially where hidden away under plastic covers
Radiator, A/C Condensor, EAS compressor, height sensors

oh the list is endless  .
Experience is the only genuine knowledge, but as time passes, I have forgotten more than I can remember
Volvo V70 P2 2006 2.4 Petrol 170bhp Estate SE
MG Midget Mk1 1962

Previous: L322 Range Rover TDV8 3.6 2008; L322 Range Rover TD6 3.0 2002; P38A Range Rover V8 1999

That sort of mileage is getting in to second gearbox territory let alone first, I can't see any way that is the original box. The biggest problem is if you drive them softly, Miss Daisy, at 30-50 mph that is prime torque converter slip speed, and will cause it to wear out quicker than at say 65 The only way that could be an original box is if it was floored up to 60 and not dropped below, or kept below 30

If you can, drive a low mileage one before, or one that has a new box... it should be smooth and hard to detect gear changes, especially under soft acceleration, "waft mode". It will give you a better idea  Yesterday I couldn't spell Engineer... Today I are one!
Inventor of the 'Guide-o-Matic automatic wheel alignment tool'
Former long term L322 owner, Up/Down graded to a Classic Tractor!

Mines at 131k and still doesn't use any oil or water. Front suspension air bags done though.

Some of the issues listed will also occur through age, so you would have to do on a lower mileage car anyway. All valid points though.

If the price is right and it ticks all the boxes go for it. I'd second the thoughts around driving a few others to see how they compare before making a final decision. Have a few pounds put aside for repairs, but you'd prob have to do that irrespective of mileage. 2011 Range Rover Vogue SE 4.4 TDV8

Previous cars :
2003 Range Rover Vogue TD6
1999 Discovery Td5 ES
1995 BMW M5 3.8 6 speed
1992 Range Rover 3.9 Efi Vogue
1992 BMW M5 3.8
1988 BMW 735i SE
1989 Ford Sierra XR4x4 2.9i
1981 Ford Fiesta Supersport

The first ffrr I drove was a 2005 with 127K, it had been chipped and drove fine, so I thought......... The second ffrr I drove had done 95K was unchipped, smoother, more power and a lot quieter than the 2005, so I brought it  Yesterday I couldn't spell Engineer... Today I are one!
Inventor of the 'Guide-o-Matic automatic wheel alignment tool'
Former long term L322 owner, Up/Down graded to a Classic Tractor!

My 04 TD6 is on 171k and still has original box

My 04 is on 130K, original box with 80% been towing horsebox with 2 up! The rest of the car however is another story......

The average life expectancy for a TD6 box is 80K, that is not to say that it is not possible to get more out of them, mine was 105K, when it went to meet its maker. Yesterday I couldn't spell Engineer... Today I are one!
Inventor of the 'Guide-o-Matic automatic wheel alignment tool'
Former long term L322 owner, Up/Down graded to a Classic Tractor!

I agree Miggit, although mine has "bucked the trend" for the OPs benefit I would't buy one without gearbox history

150K on my 2004 and I have paperwork showing all sorts from headlight wiper blades and arms, a front left air shock that was done in 2010 the right one gave out on me last month so I replaced both (to be sure) It also had all the injectors replaced at a cost of well over £2000 a few years ago although I suspect that may have been dodgy fuel (a lot of it about these parts!) other bills are for normal servicing and stuff like gas struts (tailgate) and the odd bulb here and there. Car is driving fine, most electric bits seem to work, gearbox is smooth and transfer box engages and disengages smoothly and Hill descent does what it is supposed to.

Faults would be somebody removed the aircon belt so it's not working don't know yet if its the pump or it was just removed by a tightwad to save fuel (but if thats the case and the pump has seized then it would cost more to fix than they would ever have saved) intermittent steering wheel controls for the audio and the rake adjust on the wheel has stopped working (but that does not worry me as its fine where it is) the up down bit works but again I have it on high anyway - the cruise control does not work (might be the steering wheel connections) and as the previous owner put an after market stereo in the clock shows the wrong time and the trip computer can't work either - again nothing to worry me as I never used them anyway and the advantage of having a modern stereo/satnav/mp3/ipod/DVD player outweigh any problems there.

It's almost a 12 year old car so of course there will be problems, but the rewards just speak for themselves - I've driven everything from a 1L ford fiesta to a V8 Jaguar and this is by far the best car I have ever owned so I forgive it the odd problem and sure if something big breaks that's what a credit card is for

Brian, you can sort the clock by pulling the fuse and putting it in at 12 O'clock, resets the clock to 12. Pete was going on about it in the Fitting an Android head unit thread, near the end P 25-27  Yesterday I couldn't spell Engineer... Today I are one!
Inventor of the 'Guide-o-Matic automatic wheel alignment tool'
Former long term L322 owner, Up/Down graded to a Classic Tractor!

Sort of remembered that but keep forgetting I'll set my alarm on my phone to go off at 11:45 then do it (once I find the location of the fuse that is)

Lots of good advice here.
You mention "outstanding condition". If that's the case and everything has been done, fine. If not, see above. High mileage cars are cheaper. A big "if" is whether to can get the car at a price that will allow for the inevitable repairs that that mileage inevitably brings.