GM Extended Warranty Cost (revisited)

[ASTAR]

Ok so with the warranties that everyone is talking about, does that cover EVERTHING? I want to supercharge and if the warranty would still cover everything, that would be great. Also, I want to make sure that if I extend my warranty, it covers evrything like GM would. From what I have seen, GM is awesome with warranty work. Thats a major reason I went with my Hummer over a new Dodge CTD. Doge is AWFUL about warranty stuff. I just want to make sure that if my nav screen went on the fritz, or something like that, a NEW unit would go in. i know that some warranty places reserve the right to use USED parts to make a repair!