A couple of additional tips:
If the new pump only includes a "dam" or "pocket" gasket, you MUST remove the IP timing basket, if installed. Remove the 3 bolts, pull the little basket out, and save it in case you ever need to remove the IP. If you don't remove it, the dam/pocket hits one of the mounting bolts, and won't let the pump seal against the timing cover - i.e., massive oil leak. The old/original "outline" gasket works with the cover in place. It's rumored that the basket helps contain metal parts should the pump fail, and increases chances of them staying out of the timing chain and oil pump pickup, where then can destroy the engine. So, I prefer to use the 'outline' gasket and leave the basket installed.
The catch is, if you have a very early 603 motor (prior to engine number 000602 for 603.960, and engine 002202 for 603.961 ) you MUST use the dam/pocket gasket to provide enough oil supply to the pump. Most 1986 models will need the dam gasket, most 87-up do not. Details are in this 1.5MB PDF file, on pages 6 and 7:
http://www.w124performance.com/docs/mb/OM60X/OM603_vac_pump_mod.pdf
Final note: Install the coated metal gasket DRY. Clean both surfaces perfectly, and you won't have any leaks. I've done this several times. Never use RTV here, I did once, it took me nearly two hours to fully clean both surfaces - ack! It's just not needed with proper surface prep. :p
Thanks for documenting the procedure, Hattie, nice work!
HTH