Thanks all! It WAS the capacitor. I got one from Grainger for $22
(ouch!) and it did the trick. I did learn about how those caps have a
protection device that swells the top and rips lose the internal
connections. Cool! Now I'll wait for a warmer day to check the
charge. I was pleasantly surprised to find a boatload of paperwork
including charts, part lists and instructions when I opened up the
unit. I've been reading up on the unit and how to maximize efficiency
with the proper charge. Apparently it was a very good one in it's
day.

I also pulled the contactor and gave it a once over and dressed the
contacts slightly but they were in great shape. The contactor seems
to be another major failure point for this unit according to people on
the web. No moisture ever got into the electrical area and the rest
of the unit is sparkling clean. I hope I get a few more years out of
it.