I'm going to take a stab at the oil filter...
Granted I have NO clue whatsoever, but if MB started designing the top-side filter orientation back in 85 (like the W124 E-class series), you should find it where you least expect it.
Instead of hunting underneath the car for the filter, look in the top of the engine bay for a small but distinctively cylindrical oil-filter-looking gizmo. It will be sitting right side up instead of upside down as typically found in other makes...and it WON'T say FRAM or be painted in some orange or day-glo color. Probably grey, black, or silver...
...hope this helps...
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car