im looking to upgrade my single disc and cassett in my 2003 gmc sierra 1500 to a 6 disc. I have factory bose (but it doesnt say it on the face plate), onstar and steering wheel controls. I have heard there about 10 different part numbers that were used for this radio. ive called 3 different dealers and the parts guy gusses and give me a different number each time. Which one do i need to use? and what else would i have to do to get it installed? One more thing i believe currently my onstar plugs into the auxilary port on my radio, so how would i add an aux jack at that location on the 6 disc?