Can't help you directly but I found it easier to tap wire from the 7-pin umbilical bundle. I installed a Garmin BC30 and drilled a hole above my door and ran the the wire from the camera inside. Then I tapped into the Reverse wire and ran the wireless transmitter up to the front wall of the camper (needed an extension cable).
I later added another wire from the truck's upfitter switch so that I could trun the camera on at will via the switch. I didn't want it powered all the time as then I'd have to select it from the menu all the time.. and my monitor is also my gps and my dashcam.
