Could someone clarify what is needed to install a new double din deck in an 03 escalade? I am more confused after reading everything. I don't care about onstar but i would like to keep wheel controls but it is not imperative. I have the factory Bose without nav. The local shop told me it would be $400 for the correct parts. There must be a way around this? Like aren't we talking speaker wires and power here? Thanks!