We don't have the same model, but it is the same year with the premium and video package. Our package came with a small flat screen TV, JVC (not Sony) radio, and JVC CD changer with a sub woofer and outside speaker terminals. Our sub woofer is under the couch. From reviewing the options on our trailer, there were three sound packages. Standard, then premium sound which included the Sony radio, sony subwoofer and sony CD changer. Them premium audio visual which changed it to JVC and added a TV.
I believe that wiring harness plug is an automobile standard. My new radio came with a new harness, but I didn't use it. I just plugged the existing harness into the new radio. I might still have the harness that came with the new radio.
BTW, the wiring diagram I have is for the Sony radio and CD changer.