Volvo 240DL Wagon, 1989

Awhile back, I noticed that my engine block had a significant amount of oil on it, and it was determined to be (by myself and a few others) to be the valve cover gasket. After checking a few other things (tightening the bolts to make sure it wasn't a simple problem,) I bought a valve cover gasket. I was cautioned by a friend of mine, a far more frequent poster on this board, to check here first to make sure if there was anything I should know. My questions are below:

1) The symptoms in full are described as a significant amount of oil that appears to be emanating from the seal around the engine crankcase (valve cover) and dripping down over the rest of the engine, with a lot landing on the exhaust manifold and smoking (the original way I noticed this problem.) It doesn't appear in terms of measurement to be a huge amount of oil, however - I had to drive 140 miles after I first noticed and was still above the refill mark, although not by much, compared to the amount of oil that appeared to be burning off.
Are there any other known common causes of these symptoms?

2) What are the procedures for replacing a valve cover gasket (this is what my friend asked me to post about..) i.e. is there anything required in this besides taking off the top of the crankcase, replacing the gasket, laying down a small amount of oil on the gasket, and replacing the crankcase top?

Myr