For those of you who don't speak Russian, if you click in the link in 1998K's post you will be presented with a list of cars. Obviously click on Mercedes-Benz. In the right hand pane, underneath the red Mercedes-Benz in English you will see four links in Russian. Click on the second one down (the one with the second word beginning 'cxem'). Then click on the 'Mitchell on Demand' link. You will then get some drop-down boxes to choose Year, Model and System Wiring Diagrams.
The diagrams seem to be for American models and don't include everything, but nevertheless have some good stuff.
Other links (feel free to explore) lead to diagnostic plug pinouts and codes, and to circuit diagrams for various modules such as fuel injection.