65 injector pump seals?

I have a MF 65 diesel that's gaining oil. No water loss or signs of water in the oil so assume diesel fuel. Changed out the lift pump which slowed it down (and the new pump doesn't 'leak off) but still gaining some oil. The only other places I can think of are a pump seals or injectors. It starts great and doesn't smoke so leaning toward pump seals. Are they 'easy' to change out on this pump (Perkins diesel) or do you have to go deep enough into the pump to need to send it to the pump shop? I don't mind doing external things on an injector pump, but if it's internal it's usually beyond my experience/tool set. Anyone out there changed the pump seal himself before and did you regret doing it?

Thanks in advance for help.

Bob