99 Monte running hot

Hey, this cars gauge shows it hot even after it has sat for a while. Is this a thermostat problem? If so, hows the best way to locate it and replace it?
Thanks

follow the upper radiator hose to the engine, and there you will find the T-stat. It's easy on a 3800, not so easy on a 3.4 or 3.1. Bleeding the cooling system of air after changing the t-stat on those two engines is a PITA!