My dome light doesn't work, and I've isolated the problem to either a bad ground going through the main light switch, or that the rheostat fails to engage ground when turned full left (full bright on the dash dimmer.)

How do I remove the light switch from the dash? (The shop manual has no detail on this subject, only wiring diagrams.) It is extremely tight against the dash wall.

Any recommendations on how to verify the rheostat works properly? No problems with the dimmer, only switching to ground.

Bill