OK here is the latest update.
While I haven't had the chance to bring the car back to the original mechanic, my daughter has been driving it, and as I said before, it never gets above about 120 degrees on the gauge. This keeps the high idle engaged much longer than needed, and I am sure as the car is getting betwen 13 and 15 mpg wasting gas.
Since it is cooling off a little around here, we have been driving without the AC for a couple of days, and while the op temp is now the same if not COOLER, I have noticed that the radiator cap never gets hot--even after 1 hour of driving. It gets warm but never too hot to touch. So this leads me to believe that the sending unit may not be the only problem.
Any ideas? This 5.7 should warm up to the 195 setting on the thermostat shouldn't it?
Thanks.