I have purchased a 1997 cadillac catera with a cassette deck. I want to upgrade to either a cd player/cassette combo or a cd changer. I need to find out where the wiring harness is in the trunk for the cd changer and what types of changers will work (also what the harness looks like). If I buy a cd player, do I have to have it programmed by cadillac, do I have to have the exsisting radio programmed if I upgrade to the cd changer??? HELP!!!!!