fuse. should most likely, 90% be the fuse. i forget if it was in the engine compartment or underneath the steering wheel.
The map lights are linked to a common power source and return. The regular bulb may have just gone bad or is loose in the socket. You really need to have a voltmeter and an ohm meter to check for power and continuity.It still boggles me why only 1 of the map lights would work. It would seem to be that they would be linked.