[StickMon]

The current limiting for the LEDs is built into the light, so you can run it directly off 12V.
The transistor acts like a switch. Where it says "30" is the voltage source.
The transistor will be open when the light's off, closed when it's on.
The little rectangle above it is a small value resistor that's used to measure the current going to the bulb for the sake of the bulb out warning.

I think Samuel established in post #8 that the light is good, just not getting power.
Next thing would be to get at pin 16 on the back of the Light Switch Cluster, where the black/yellow wire comes from, and see if there's voltage there (with the brakes on, of course.)

If not, it doesn't look good for the Light Switch Cluster.