Hi all,
I recently redid the tailgate wires. I bought the wire harness from ECS tunning. I think it was about $160.00 for each side. I used the installation guide from BMW (see attached). The job wasn't difficult, but it was tedious since my hatch wire had failed and i didn't have a way to open the glass portion!! I ended up cutting out a piece of trim to get access to the glass lock and pop it open using a small screw driver (there is a video out there on this).
The wire installation guide made it easy to figure out which wires go where...so hopefully it would help you DIYers out there. everything you would need is inclusive in the ECS tunning wire harness and no need to buy anything else.

Regards,