Gizmodo has a guide on how to not get ripped off by your mechanic. There's some good advice there, check it out.
A little busy watching Sebring right now, but I can say one thing for certain. If you purchase from a dealer, and keep a solid history with that dealer, the manufacturer will stand behind you, (depending on the manufacturer,) sometimes for life. Car makers love to see you visiting their dealers for service, and not only because it keeps dealers happy. Manufacturers back their dealers with the latest of everything, and visiting them shows you care about your purchase. If you think you are getting overcharged at a dealer, choose another nearby dealer and explain it to them. But DO NOT underestimate a complete dealer service history. You can even use it for leverage if you have a problem in the future, with the dealer and the manufacturer. They will back you with assistance as I said, sometimes for life.