Your ground should be coming from a single wire from the door jamb switch, usually white wire I believe. Also, 1 of the leads off your headlight switch should also be a ground that is also white and gets 'closed' when you rotate the switch handle all the way (like when you dim or brighten your instrument lights) - all the way usually turns on the courtesy light.
Do you know anyone that owns a volt/ohm meter and do you own a simple electric test light?
The other ground is the wire coming from the door jamb switch, you can use the volt/ohm meter to verify continuity with the car body(ground) which when you open the door, the jamb switch completes the circuit between the wire and the body - thus producing a ground that is connected to the light.
You would use the test light to verify which wire into the courtesy light has power all the time, which it should have once you put that particular fuse back in, that way the lights come on when you open the door and provide a ground to your light.
Sounds very complicated I know, and is probably just my poor explanation.
Do you have any other members nearby or just someone that generally knows about mechanics and auto electrics?
Also, I have seen other members on this forum that have a knack for explaining things very simply. I've finally understood things that have been unclear to me for years.
HOPEFULLY, someone else will read what I've said and either verify that I'm telling you correctly or be able to explain it better.
