I understand your frustration. I went through something similar with my '96 E Class. But MBDoc is right, not all dealers are bad.
You have an opportunity here to help not only yourself, but all MB owners and future buyers in your area. You can take advantage of this opportunity by calling 1 800 FOR MERCEDES, ask for your area representative and DEMANDING satisfaction. If they have to give you a new car so be it. But you MUST let MBUSA know what kind of BS you're getting from these people. I raised enough you know what in '96 that I ultimately got things taken care of.
Keep us posted about whether or not MBUSA takes care of this. If they don't let us know, we have enough people here who don't want to see this kind of thing, we can absolutely tie up their switchboard with complaints until they do something about this.
Good luck and Merry Christmas,