Well...you have a few options. The easiest is to examine the oil, if you have not already. Is it chunky? Is it pretty and sparkley? Either is bad.

#2 would be to strip off the front dress and cover and pull the oil pump. Any ovbious failure? Spin it before you pull it and see if you get oil to the head.

#3 is probably a bit more involved, but pull the oil pan and take a look.

Heck, if you are not getting oil to the head (you should when cranking by the starter), then pull the valve cover and look at the cam. Pull a fe of the bearing towers and take a look. Oil starvation will be ovbious and if it is an oil system problem, the top end is a likely place to see it first.

Do some investigation before you take it to a shop. It may save you some $$, or at the least, you will know what the problem is before hand.

Good Luck,
Michael