I've gotten loads of free advice from this and other forums. Now it is my turn to share some guidance.
This past May I replaced my original leaking fuel primer pump. It is a simple painless operation that took about 30 minutes - 15 of which was spent taking the attached pictures.
The location of the existing fuel primer pump (next to the injector pump).
The updated replacement part - I paid about $30.00 from a dealer simply because I was on travel and did not want to wait to find it cheaper.
Use a hose clamp (I used vise grips) to close off the fuel line after the first stage filter (the clear one).
Using a screwdriver, loosen and remove the fuel hose.
Using either a 17mm or 19mm socket with an extension, remove the fuel line fitting.
Setting the fuel line fitting aside (on top of air filter)
Now you have room to access the old primer pump
Remove old fuel primer pump with a 24mm open end wrench (note pinched off fuel line at bottom of photo.
The new and the old parts compared. The new part came with an adapter that was not required in my application.
Clean up and ensure you have removed the old copper washer.
Install new fuel primer pump with a 17mm or 19mm open end wrench.
Replace the fuel line fitting, tighten, and enjoy the completed project!
Next I'll work on posting my project of adding rear headrests. I did this in under an hour with used brackets and leather headrests I got from mercedesdismantlers.com out in L.A. for under $100 - shipped! If done properly it will be no different than if it was factory installed.