I find the Injection Pump as #603 070 32 01 for OM603.970 1990 + up 350SDL. I'm not sure of the "pin" as I have not had the oppurtunity to delve into the pump but I assume it is part of or nerby the delivery valve seals? The parts diagram i have shows some detail but?
Price is dependent on "need", if you "need" results now, today , or yesterday, or not. If you need to be rolling then the options are Rebuilt(usually core swapped) , rebuild (diesel service rehabs your machine) or used or $1500?,$1000?, or $500? If you've got the time to work on the solution and you want to expand your capabilities - you could start looking around and asking around and you could pick up a good used one and DIY to gain a better understanding of diesel ephemera!
You can follow this route to sucess:
Need Injector Pump for 300 SDL
OM 603 injection pump problems
But if not then try a reputable shop with a good warrantee of their work and pay their price for the piece of mind. Good Luck!