it was all plug and play. only difference is he has grounded the handbrake cable so the video etc works. (wasn't sure if this was a live) we removed the head unit, harness, heater controls and ribbon and still had the high draw down
there was a dent in the ribbon cable about the size of a match head but I used the meter on ohm to check for continuity between the pins and it showed that the insulation was intact and once it was the removed the high draw down was still present