The plastic guide pins are in both n/a and supercharged 5.0 engines, they just tend to wear quicker in the supercharged. It's about a $3-5k job depending on where you go, but the shop needs to have purchased LR tools for the job, or designed their own. A very late model 2012 might have the upgraded timing chain guide pins from the factory, someone on the forums posted the exact TSB with VIN numbers of the affected RR's. $8k for the extended warranty sounds like A LOT.
