You need to drain the coolant and pull the lower radiator hose. The thermostat housing(where the lower rad hose connects) is just bolted on. You unbolt it and the thermostat comes out. If coolant is spewing out of the area around your header, then your headgasket may be leaking from there, in which case you would lose a lot of coolant, but you may not necessarilly see any smoke coming out the exhaust.