It looks like I have an oil leak from the bottom of the injector pump--what should I look for and how hard is this to remedy?

Degrease it and see if you can find where it is leaking; I like to use brake cleaner but other stuff works.
There is a few threads where Members have had a leak down by the Throttle or Shutoff shafts (there is just and O-ring and washer that seals the shaft/s).
If your IP has a Cover on the side that can also be a source of a leak as can the front of the IP where it bolts to the Block.
No one so far has reported an Oil leak there but where the Fuel Supply Pump Bolts up to the IP is another possible.
At the below EPC parts type site pick your chassie and model number and see if you can find the Diagram with the Fuel Injection Pump and this will give you a better idea.
http://www.detali.ru/cat/oem_mb0.asp?TP=1

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84 300D, 82 Volvo 244Gl Diesel

Thanks for that. From the looks the the diagram it appears that my chances of a repair without removal of the ip ( and timing afterwards) is pretty good.
Is the bottom half of the pump basically bathed in oil from the chain galley or does it come through a pressurized tube?

I was not able to find info as to how your IP is lubed. On mine there is an external plastic tube that goes from the IP to an area near the IP timer gear connected with little Banjo Bolts/Fittings.
But, when I looked at the part site diagrams (you have a 201.122.85 190D) I did not see any external Oil Supply Tubing. It could be that there is an Oil Supply passage down the center of the IP Camshaft fed from the IP Timer Gear, and a hole cross drilled hole further down the cam to dump the oil in the IP. But, it drains back into the Timing Chain area (but I am guessing).

There is an O-ring on the Drive end Of the IP but you would have to pull the IP out to change it.
That is why it is better to be really sure where the leak is or you can end up fixing the wrong thing.

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84 300D, 82 Volvo 244Gl Diesel

Where can I find the part number on the injector pump of my 1998 E300d?

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1998 E300Turbodiesel
1980 300d

Ready- Ronnie

The Green Arrow points to the little Plate that I believe has the Bosch Number and the Mercedes Number.

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84 300D, 82 Volvo 244Gl Diesel