Reporting success on installing a new battery selector switch! The old switch seemed to be fastened on with "a lick and promise" as my dad used to say. There was a partial bead of something yellow with age around the back rim of the switch, but the main holdfast seemed to be the post for the switch. After I removed the wires from the back of the switch, I could easily click it from stop to stop by holding the body of the switch while the post remained stuck in the panel. So apparently it was the post that was sticking things up, not the internal parts of the switch. I ended up partially Dremeling and then drilling the post out, and the switch body fell off the back of the panel. (see photo)
My local marine consignment store had a dozen or so battery switches. All but two were as sticky or stickier than my old switch. I took the better of the two remaining choices, but it had a panel screwed to the front that was too big to fit on my panel. I couldn't get two of the four screws holding it off anyway, so it was back to the consignment store with that one. Closer inspection of the remaining stock revealed a switch of exactly the same model as my old one, with a different handle but an easy motion from stop to stop. And only $18 compared to $50 for the first one! I rigged up four bolts through the panel and grommet-type clamps on the body of the switch to hold in in place, reconnected all the wires, et voila! Everything works except the AM/FM receiver and tape deck. (Tape deck! Ha! That shows you how old my boat is.) I must have jostled that wire. I didn't intentionally disconnect anything but the switch. I'll look at it later. I only get about two English-language FM stations and one AM station anyway at my slip. The engine starts, too. Always a plus.
I didn't take a picture of the new bolts securing the switch, but can if anyone is interested.
Wishing you equal success on your projects.