Your switch is probably salvageable, the electrical switches in cars from this era actually need to be used to keep them in good order, moving the switch cleans the contact area.
If I were in your situation I would clean all the terminals from the headlight itself right back to the switch with special attention to the grounds. There are a few good How To threads in the archives on dismantling the switch and cleaning it, it is also the only way to know how bad the heat damage is. After you get the headlight system working properly again you might want to have a look at the rest of the terminals, grounds and switches in the rest of the car, they have had the same lack of use so probably have the same amount of oxidation on them.