Check out www.hitch-web.com
They sell several different trailer hitches for most all cars including MB. For each different hitch they sell, you can download a .pdf of the installation instructions. Perhaps some of those installation sheets would give you some ideas you could use to fabricate a hitch from local materials.
2004 C240 Wagon 203.261 Baby Benz
2008 ML320 CDI Highway Cruiser
2006 Toyota Prius, Saving the Planet @ 48 mpg
2000 F-150, Destroying the Planet @ 20 mpg
And remember folks, Only You Can Prevent Hilliary.