My RR suddenly started severely misfiring when going down the highway and the engine check light started flashing. I pulled over and scanned for codes and found the misfire code (at that time it only showed misfire for cylinder 5). I was only a few miles from home. I pulled out the ignition coil of cylinder 5 and found oil at the bottom of it. I looked inside the spark plug well and it was filled with oil.
I started removing the oil from the spark plug well and cleaned the coil in hopes it would fix the misfire.

I started the engine and it started misfiring immediately. I looked at the freeze frames and was shocked to find that there was misfire detected on cylinders 3 and 7 as well (no DTC for these were ever present). Turns out the cylinder 3 is misfiring lot more than 5 and 7. Haven’t looked inside the cylinder 3 spark plug well yet but I am thinking it must be the valve cover gasket thats leaking causing the oil to spew into the spark plug wells causing a misfire.

I do not have the confidence to do this repair myself. I was wondering if anyone has any idea how much it would cost to fix at the dealership. I was thinking getting both sides replaced.

Any input would be greatly appreciated.