Well, first of all, you need to find the right deck you want to install. I'd recommend www.crutchfield.com You can enter the year, model, and options for your car and it will give you the things that fit your vehicle. Go to car audio & video and scoll to find what fits my car. You might have to buy a kit so it will fit in your dash. When I got a CD player for my 1985 Volvo five years ago, the player didn't fit becasue of the fact that the deck was smaller than than the place where it had to go. So it was like 12 bucks for a kit that fits the shape of the slot and the deck. Also check out xmradio.com to see what they have for xm ready decks as well as direct connection. I have the Delphi SkiFi 2, but have not installed it, and won't for another few weeks. I hope this helps.
almost all decks fit in the sorento. even some of the Double Dins. u just need to make your own mounting kit for it. but for the single din stereos, i think crutchfield sells a kit that works fine with the sorento