Thanks to googling and posting this group I got a lot of good learning on diagnosing and repairing my water system. After eliminating all other possible causes, I finished installing the new pump around midnight yesterday. Had to update the wiring all the way back to the box as well, since the old, cloth-wrapped wire was a real fire hazard. I made a lot of stupid mistakes, concluding at 9pm yesterday with dropping a terminal screw from the pump's switchbox into the sand, never to be seen again. Sure is nice to have water though.
The pump and all related piping and consumables ran around $400. Considering the cost of my time, it would have been cheaper to call a plumber last week. Maybe not - I wonder what a plumber would have charged for a job like this. But as they say on the MasterCard ad: learning how to do major plumbing work myself - priceless.