Replacing the Thermostat on a VG30ET
1: drain the coolant by unbolting the coolant temp sensor at the bottom of the radiator. It will have two wires coming out of it just follow them up and unplug it.
2: unscrew and remove the hose clamps from the small hose thats connected to the thermostat housing.(this is a good time to replace that hose because they are known to leak)
3: now remove the hose clamp that connects the hose to the radiator. then romove the hose.
4: there are 3 bolts that hold the housing together. Unbolt those and remove the top half of the housing. You might have to scrape off some gasket sealer around the outside of the housing.
5: now switch out the old thermostat with the new, and replace the gasket.
6: now do everything in reverse.