Leak at base of injector

I have a recently purchased 300 TDT with 150K. Two injectors are leaking at the base where they screw into the head. It is a black oil type leak and the vent hoses or body of the injectors appear to be fine. Is this common or uncommon? I assume that I need to remove the two offending units and replace a seal, correct? Are leaks at the remiaining 4 injectors likely, if so, I will take care of the rest at the same time. I have a socket that fits, but do not know the torque. The engine runs great (hot or cold) so I assume the injectors are fine. If I need to do any checks or inspections while I have them out, please advise. I have a spare car so If I need to send them off for cleaning etc, it is not a problem.

I really like the forum and contribute when I can. Thanx in advance to anyone that replies!

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Deezel
87 300TDT
150,000 miles

[Benzmac]

There is a small metal washer at the base that is most likely worn out. There is a spec on the torque. If you are going to be working on this alot, I would get the CD. We have them in the partsshop to the left of the screen. The CD will have all of the tech you need. You will need the 124 CD.