I've had 3 GPs that I've changed the head unit in. 1 was Monsoon and the other 2 were not. I use crutchfield.com for the correct part numbers, but I have found that I can get the dash kit, wire harness, & antenna adapter cheaper on Amazon, assuming you have an account. I have also replaced all the speakers in the cars for the most part. Monsoon speakers are component-based, so you can't just throw a 3-way or 5-way 6x9 in the rear deck. It needs to be "Monsoon-style" and the woofer & tweeter are powered separately. Anyway, if you are just replacing the head unit, it is fairly easy. Just need the dash kit, the wire harness kit mentioned above to retain chime, and the antenna adapter. Good luck!
