How do I change the thermostat

Need to follow the upper radiator hose back to where it enters the engine block. There should be a housing there with 2-3 bolts which you can remove to access and replace the thermostat. You may have to remove other engine components to access it.

depends on what motor you have in the vehicle. If it has the 3.4L V-6 , it is fairly labor intensive to change it. Sometimes it is easier to remove the exhaust crossover pipe to make easier access to the thermostat housing and bolts ( drivers side of engine between the cylinder heads )

On the 2010 3.5L V6 transverse mounted engine the thermostat is not on the top, but at the lower radiator hose on the passenger side of the engine. You'll need a deep 10mm socket, two bolts. One word of caution, make sure the rubber gasket is of good quality. I bought a Murray thermostat and it had a cheap rubber seal that did not seal up, tried twice. Had to buy a seal from NAPA which was much thicker and more like the original.