Hot temp. gauge should I take to shop? See detail below

If you have not done a full cooling system service in the last few years it is probably overdue.

Absolutely have this looked at! You could be looking at an early warning sign of intake manifold gasket failure. At your current mileage, your due! GM 3.8L V6 are notorious for upper and lower intake manifold gasket failure. Look for coolant pooling on the top of the engine. If that's what's going on have it repaired ASAP. You do NOT want to reuse the plastic upper intake manifold (upper plenum). They crack. Replace it! Get the SECOND design Fel Pro Problem Solver intake manifold gasket set. If the lower intake manifold can't be reused (most likely it can be) get the AC Delco replacement. The Dorman version will not fit. Hope that helps! Jim