Instrument panel and Radio lights

I own a 200 Chevy Impala LS with the 3.8L V-6 and
I need to know why my instrument panel and radio control lights are not working. I have already check all the appropriate mini fuses and made sure my dimmer switch was in the correct position and all those things check out fine.

About a year ago my instrument panel lights on the right side of cluster were about half as bright as the left side and now today I don't have any lights on the cluster or radio except for the warning lights that come on at start up and the clock and radio station are at their dimmest. All of my other lights in and out of the car all work normal.

There are two dimmer switches for this car, one is the actual headight/dimmer and the other is a instrument panel dimmer switch (module switch) in the dash some where. Do you know which one I need to replace first? I'm thinking the latter of the two.