Hey folks. I've been doing some research for this issue. Though true you can order the OEM wiring harness for a small phenomenal fee, there are two other not so easy to acquire kits.
1) Brink/Thule P/N 727173 only available in Europe and no one seems to want to ship.
2) Bosal P/N 008-098 same issue.
I have to ask at this point, why the heck is it so difficult to find a wiring kit for a ten year old Mercedes?!?
Also is there anyone on this forum who would be willing to purchase and ship me a Brink kit???