I have the 3m Scotchgard pro hood, fender, mirror and door kit which has a 7 yr warranty. I've installed it on just about all of my vehicles and never had a single issue.
Installation is pretty straight forward and not difficult at all. If you order the kit online you'll get a free installation kit and a short how to video that's very informative.
Forget the 3-600$ price quotes from your local shops, pretty sure I paid around 110.00 shipped for my Denali.