1992 Mercedes Benz 300d fuel injection pump "o" r

1992 mercedes 300d, 5 cyl. 2.5 engine fuel injector pump "o" rings are leaking. What is the procedure for removal of everything necessary to get to the rings? What parts (i.e. manafold, lines, etc.) need to be removed and once removed using the 32 point socket and the "O" rings and brass rings are replaced is there any calibration necessary?

i was told this is not a do it yourself project because the pump needs to be re-calibrated. These are only "O" rings and nothing in the pump mechanism is being disturbed.

I guess my question is, must I bring this to a dealer because it needs re-calibration or can I do this myself without difficulty?

Thanks