GOOD NEWS!
I went to Sears and bought a new multimeter and a good set of test leads with alligator clips. I came home and hooked them up to the alternator output post and a decent ground and fired her up. The volt gauge on the dash showed in the yellow, so I killed the master switch and turned it back on - it went to red (overcharging). I ran out and checked the voltage - 30.4v. I turned the adjusting screw slowly until I felt a point of resistance, then turn a little more. It dropped to 29v. I turned even slower and it dropped on down. I finally stopped at 27.9v - WOOHOO! I checked at the batteries and got the same. I went back in and switched the master power off and back on a couple of times and she was in the GREEN, slightly below the tick mark. FINALLY! I buttoned up the alternator and lowered the hood and went for a ride around the field.
While I was out working on her, I decided to try a jumper wire (with alligator clips) from the fuel gauge to a good ground. Yeah, that didn't help. Oh well, at least I got one problem solved! Good enough for me!
I went back into the cab and fired her up one more time to take in my victory. WTF! The volt gauge was showing in the red again - all the way over! I switched off the master power and switched it back on a couple of times - it went back to slightly below the tick mark in the green!
What's going on here, if I might ask? I think I am going to try to find another switch - mine is pretty loose and easy to switch on and off.