Quick fix? Don't know. Did you take apart clocks as a kid? Or, more importantly, did they work correctly after you put them back together? Quickly?
That throttle spindle there, the shaft has a groove in it further down where an o-ring sits to seal it in the bronze bushing. That is probably what is leaking. Not that hard to replace, but you MUST KEEP EVERYTHING CLEAN CLEAN CLEAN, do not let any dirt fall into the IP, as you will have the cover off. You also will want the cover gasket. The IP has numbers stamped into the side. A Bosch fuel injection shop should be able to get you the seals based on the IP numbers.
Here is a pictorial-- warning, from non-Datsun (but similar) application:
Resealing a Bosch VE Injection Pump (VW)
http://crustycrank.com/resealinjpump.htm
About 2/3 of the way down in the article, for the governor shaft seal, your immediate project.
Also important: Mark the orientation of that splined throttle shaft in relation to the cover BEFORE removing the cover or there's a good possibility it won't idle or run correctly after reassembly. Hope you already marked the orientation of the lever (the one you already removed) to the shaft also. Actually that is what is important, lever orientation to the shaft, more than the shaft orientation to the cover.
Good Luck!
