M104 valve guides
Few M104 motors are ever brought into our shop for oil consumption problems. However, we have done head gaskets on a hand full of them with well-over 100,000 miles (all of these jobs were done because of leaking head gaskets). The guides in these engines hold up MUCH better than on M103 motors, but we did put new guides in a couple of these heads. I believe one had 116,000 miles, and the other about 135,000 miles. Any M104 motor with over 100,000 miles on it that comes in to our shop for a head gasket job gets valve guide seals, though.
When was the last time your head gasket was done? It certainly will leak badly again before 200,000 miles. I don't think I've ever seen an M104 head gasket go more than about 90,000 miles whithout pissing badly out the right rear. I would say definitely do the guides the next time the head comes off.