Sorry, Can't comment on the M103 but I assume the M117 is similar. There's a grill cast into the bell housing with an opening to access the drain plug. Have a helper either under the car watching for the plug to come around or turning the engine while you watch.
Once you've rotated the engine around so that the drain plug is at the bottom, do yourself a favor and mark the crankshaft pulley so the next time you can just watch for your mark as you rotate the engine. I just used a Sharpie.
Here's the section from the manual.
Thanks for the link to the procedure, as I plan on performing this service in the near future. Very Helpful!