First, its pretty obvious that you need to grab a manual for your vehicle... There are few better investments out there....
Second, the thermostat is on top, and in the front of the engine (beside the distributor), easy to find... its housing is what the top hose that goes to the radiator clamps on to.
There are two bolts that bolt the thermostat housing to the intake manifold... the intake manifold is what the carburetor is bolted to, and it bolts to the cylinder heads...
A new thermostat and gasket will run about $7... now, it could also be possible that the thermostat housing itself has rusted through, you can pick one of them up for around $10 from most parts retailers.