For the overhead light, does it come on when any door opens? Does it come on when turning dimmer switch all the way on? Assume you replaced the bulb. First thing to do is drop the socket out of the ceiling and check actual wires at socket connection for power when doors open and switch is on. Could be a bad fixture. If I'm still no power, pull one of the door switches and see if power is coming into them just to eliminate that as a problem. But since nothing turns on the light my guess it is either the socket or wire back to central point where the different power outputs come together.
For windshield wiper, it could be switch in steering column or the wiper motor. Need to test for power again and could try continuity test with switch in different positions. But since checking contacts for power involves taking the steering column apart maybe just replace the switch and see if that fixes it.
For radio, that could be many things from radio itself to wiring to connectors. I would try running power directly to radio and see if it powers up. That would at least eliminate radio.
