Actually, you would simply disconnect the switch.
It closes to make a ground for the light. Not connected means it can't close (reach ground). Connecting the two wires will give you a constant door ajar light.
I think you will have success with the spray lube though (not WD40).
Here's how I do it:
Open door
spray latch with the straw (window up) more than you think you need to, 4-6 seconds of douching in many directions. I use Remington teflon gun lube.
Using a phillips screwdriver shank, simulate the latch post with one hand while the other repeatedly opens the door handle after each simulated latching.
Open/close the latch a few dozen times and spray it again for good measure. You can do this very quickly with the screwdriver while the lube is flowing.
Opening and closing the door is silly when you can do it 5 or 6 times manually in the time it takes to open/close the actual door.
Rag up the mess and expect some drips from the bottom of the door.
http://www.rangerpowersports.com/forum/f197/door-ajar-light-dome-light-stays-203206.html
http://www.therangerstation.com/tech_library/DoorContactPin.html