I have a GMC Acadia SLT-1 with the 10 speakers! My radio has the thin non touch screen radio. I was wondering if I can buy a used one that is touch screen. Looking at the backs of both radios I see I only have the black wires and not the grey. Does anyone know what the grey wires are for? I would assume for the backup camera since mine is on the mirror. The one I found is fully unlocked, but I would like to get it programmed to my car, how much would that be?