Nothing wrong with shopping at
Crutchfield, best online retail customer service. Easiest way to get what you want with everything you need to complete the install correctly. Pick the double din you want, call them up, and they'll make sure you have everything you need, and you get a warranty and detailed instructions. It's darn near foolproof. better than any online forum.
If you use them, buy from them.
You'll need a GMOS adapter, runs around $100, in order to interface with the Class II Data Bus. They can tell you which one. You'll need a mounting kit as well - Metra or Scosche have them for each vehicle.
If you have specific questions or want to know why/how something works, feel free to ask us. Be sure to read the manual first. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
Going to your local shop for information then buying online is a bad move and the reason the industry is suffering. I never recommend that and shake my finger at those that do.