okay - i checked my records - i bought mine (83 diesel Van) at 37K, finally did
valves at 50K, a couple were tight, havent changed any since (now at 80K) - 
its really not a bad job,m my guess is your valve cover is leaking oil anyway,
so take it off and while you're in there check the valves at least (of course
once you see what they get you for a valve adj you'll see the economics
of buying the tools and doing it anyway.)

right on the money chris - take care of that injector leak (make sure thats what
it is !) before you play with anything else - BE CAREFUL around injectors - spray
oil at 1000 psi or something like that - very DANGEROUS - if you get it under
your skin they cut off the affected part, so says Poor Richard.

I would try putting a new injector heat shield, maybe ??

sps