Leaking Injector Pump

[buschy03]

Need some help here,,, have a rotary injector fuel pump on a 1985 3B, that is leaking from the top of the pump around the ( don't know the proper name), so.. accelerator shaft ,where the spring and main pull shaft is connected on with a nut. Is there a O ring in there that is buggered, and how tough is it to get that fixed,,, any suggestions would be greatly appreciated.