PROBLEM FOUND: clogged radiator.
I just called the service shop and the guy told me the radiator was almost completely colgged.
That is frustrating. I have done a good job of keeping the system refreshed with good antifreeze - or so I thought!
At any rate, glad it was nothing internal.

Also, I hope this experience might save others some hassles in the future.

Smokey, Mine didn't "act like it was hot". By that I mean it never boiled over. But, if you wait for that to happen you risk serious damage. Tell your friend to have his radiator checked.
One sensor does provide data for the analog gauge, the other sensor supplies data to the computer.

edit to add: I am back at work now with my truck. Everything works fine. The guy at the shop said there really isn't anything I could have done to prevent it, nor anything I can do to insure it won't happen again. Apparently it is static and/or galvanic caused.
Whatever, I can run 65 or 80, A/C on or off, and the temp sits at 97-99 deg C.
For only $155 repair, I am happy!