P38 Stereo Wiring

I am having stereo issues. Looks like at one time there was an aftermarket deck in my rover. Currently I have 3 speakers not working. Does anyone have a wiring diagram for the factory Alpine Deck? I also have an Alpine NAV module installed, and it looks like it is not supposed to be there based on the wire counts, does anyone have info on this as well? I also noticed that when I have the power plug out of my radio I get a humming noise from the speakers. Is this typical?
Thanks, Scott