Ouch! I just priced both an M Class and R Class and the M Class starts at $40K and the R Class at $48K... Don't think I can afford that or just the engine itself. Why are they so expensive? I think a VW TDI is the best route for you to be honest, since they're quite modern, easy to find, and are really reliable. I'm still looking for an iMark 1.8L diesel though since I'm not sure if a TDI can be easily adapted to RWD and lateral mounting.
edit: The following question was in reference to the Isuzu diesels, not the VW ones, I know they're reliable. Does anybody know if they're reliable or economical though (the Isuzu ones) and what MPGs can be expected in them?