The thermostat housing on a 1995 Corolla is located on the end of the engine, drivers side, near the top, but just below the distributor. It is at the upper end of the radiator hose that connects to the bottom of the radiator. It also has a temperature sensor and wire connected to it.
Start by draining some of the coolant out of the radiator into a pan or bucket. There is a petcock valve at the bottom passenger side of the radiator, open it a few turns until the fluid starts draining. Keep it awayy from pets!
You don't need to disconnect the radiator hose. Remove the two nuts from the thermostat housing (10 mm socket). Carefully pry the housing cover, exposing the thermostat. Remove the thermostat, you may need to pry it out or pull with pliers. Also remove the rubber gasket.
Make sure you use a new thermostat and gasket. First install the gasket around the perimeter of the thermostat (there is a groove in the gasket). T.hen seat the assmbled gasket and thermostat into the housing. If the thermostat has a "weep hole", it is best to orient it at the top.
Install the nuts, and carefully tighten, alternating from one to the other to keep it even. Tighten firmly, but don't overtighten. Put your coolant back in the radiator, make sure the radiator cap is tight. If you have extra coolant, put it in the coolant reservoir. Start engine and check for leaks! Your done.