Hello dear Range Rover friends!

Sorry for my poor English.

I have a 2010 LR322 TDV8 272hp.

I was on vacation last weekend and drove up a steep hill with lots of curves. The drive took about 25 minutes. When I arrived at the parking lot, I noticed smoke in the engine compartment. I immediately opened the door and saw that the expansion tank (coolant) was boiling and the coolant was pouring out. My entire parking space was covered in coolant. I let the Range Rover cool down and hiked up the hill. After I got back, I got water from a pub and topped up about 2.5 liters. My first stop was the gas station, where I got 2 liters of coolant. I filled it up to the max and then drove about 400km home. I checked the tank several times during the drive to see if it was leaking, but it held the coolant and it didn't boil over. What's interesting about this story is that the temperature gauge was within the normal range when I drove up the hill, but then the fan didn't turn on in the parking lot. But it's working now.

I'm planning to replace the expansion tank anyway, as I've heard several times that it's causing problems. Do you have any tips for me on what else I might need to replace?

I'd also like to change the coolant. I've already topped it up with a G12+. Is that correct?

Thank you in advance for your answers.