Im buying an aftermarket headunit and was wondering if i absolutly need http://www.crutchfield.com/p_1272RGM11B/PAC-GM-Radio-Integration-Adapter.html?tp=3486 that to make it work.. I dont care about the chiming or the tripodometer. And i couldnt find any other wiring harness for the car. I also want to be sure i dont lose my factory remote start! Thanks