Thanks supersabre, amazingly enough I did know that about the ohm ratings for the gauge and for the sending unit. :-) However, one question I would ask is did that grounding out of the sending unit wire just test the gauge or does that mean that the voltage regulator is also okay? I am guessing that it is just for the gauge.
If I replace the sending unit, right now my plan is that I will replace it with an auto meter unit and an auto meter gauge, as I don't really like these SunPro gauges anyway. But that's not something I planned to do in the near-term, instead trying to focus on the things that might make the truck more safe, like brakes. :-)