Well here is how I went about it. I first went to NHSTA.gov,(not sure if that's exact address) anyhow did a complaint search and turned up at least 3 formal complaints to the federal gov about wiring harness failures on those model years M104 engine cars ranging from stalling in traffic and causing accidents to full blown vehicle fires. Then I went to www.mbca.org,
the car club and did a search and printed out at least a dozen complaints from car club members with the wiring harness problem, I also printed out about a dozen or so threads from this list.................I was adamant with the service advisor(being a fireman and pointing out several "code" violations in the shop probably didn't hurt either). I got a call on my cell phone within a half hour that MB would pick up the tab for the part, along with profuse apologies.
Best of luck to you