Sounds like a M606 engine maybe? Under the plastic engine cover are the injectors and fuel return lines.
The oil filter housing is still located at the left rear of the engine. There is a plastic top that takes a large socket to remove. Do not over-tighten when reinstalling!! The torque spec. is maybe 10-15 Nm. As with all MB with the filter on top, loosen the filter before draining out all of the oil.