Janet --

The plastic cover does tend to stick. If you look closely you'll see a tiny recession the edge opposite from the switch where you can insert a small screwdriver. This lets you pry the cover down from the headliner and off its clip. (It often sticks to the plastic headliner, particularly after 22 untouched years.)

Once you've popped this edge down, the cover slides over the switch -- that is, toward the passenger side.

The switch assembly is held to the roof chassis by two screws.

You must disconnect two wires. One is power.....and if it touches ground, you'll pop a fuse, the other is the wire goes to the door jamb switches. The wires are color coded, and have different sized tab connectors, so they only connect one way. Note also that one mounting screw acts as an electrical connection to ground.

Try to scrounge a replacement light assembly from a later car -- say, '85 or '86 or '87, which is designed with a slightly shorter, fatter, and stronger switch lever. These pictures show a light fixture from an '87 car that was installed in an '82 just because the lever snapped.