How do you change the thermostat in a 1997 Subaru Impreza sedan?

raise front of car to work underneath, on bottom of engine just behind radiator youll see the aluminum thermostat housing with large water pipes attached. just un bolt it and with a basin or something below to catch water, prise apart slowly and allow to drain then pull out old stat, note which way round it fits in hole before you take it out. the seal is attached but new stat should come with new seal. stick it in tighten up housing. top up your water and anti freeze, pour slowly to aviod any air locks. start up leave to idle for while; check for leaks and if water is circulating into expansion tank, top up fluids if required.