When I posted that thread (linked by yal), I had contacted MBUSA as well and they mailed me back that I had to be aware of the fact that a lot of US MB dealers would refuse to work on a european mercedes. MBUSA does not support the mercedes models that are sold in the rest of the world.
Just how different can those models be???
Anyway; the fact that MBUSA doesn't want to work on european cars is probably one of the reasons why people are not interested in gray import benzes.