Now, before I go into the procedure, I must emphasize that you should ALWAYS pressure test or replace the radiator cap when replacing the thermostat AND pressure test the cooling system to make sure there are no leaks.
At the minimum, test it. It's cheap and will save tons of headaches later.
BTW, for those who want to know, I prefer OEM radiator caps.
Remove the air cleaner and duct assembly.
Drain the coolant until the coolant level is below the thermostat.
Remove the crossover exhaust pipe.
Remove the radiator hose from the thermostat housing.
Remove the thermostat housing bolts and clean any sealer from the bolt threads.
Remove the thermostat housing and gasket.
Remove the thermostat.
Clean the mating surfaces.
Install the thermostat.
Install the thermostat housing and gasket.
Install RTV sealer (GM P/N 1052366 or the equivalent) to the thermostat housing bolt threads.
Install the thermostat housing bolts.
Tighten the bolts to 25 Nm (18 ft. lbs.) .
Install the radiator hose to the thermostat housing.
Install the crossover exhaust pipe.
Install the air cleaner and duct assembly.
Fill the cooling system with appropriate coolant mixture.
Inspect the cooling system for leaks. Repair as necessary.