Well, I think I'm making progress...
I disconnected the transmission fluid output line at the radiator and fired it up in neutral. Fluid came out a little. It was kinda frothy with quite a bit of air in it and came out in spurts. When I put it in drive, it became a solid stream of fluid and the car moved forward a little. I shut it off right away and reconnected the line. I then restarted the car. This time, I dropped it into gear and nothing. I'm thinking the trans fluid is low now though since I dropped about a quart in the drain pan doing the test. I had to stop for the night, but when I get home today, I'll refill the trans and give it another go.