I replaced my head unit with a Koolertron aftermarket unit with a backup cam in my 2004 Grand Cherokee (WJ) and I'm having trouble hooking up. I do not have direction to go by. is there a hookup to the transmission to tell when the vehicle is in reverse? I have two cables coming from the backup cam I believe they are video and red cable possible a power cable it has a red and black wire coming out of it. Can someone help with the wiring???