Phaeton :: Rear Cabin Light System Stop Working

The cabin light system in the roof for the rear passengers stopped working in my car a few weeks ago. The red ambient lighting that lights up the buttons still works, and one of the buttons lights up yellow (the one that controls whether or not the lights should turn on when the doors are opened). However, pressing any of the buttons has no effect whatsoever (although it did momentarily light up one of the side lights once or twice). The big cabin light and the two reading lights on the side refuse to light up.
According to my local Phaeton Center, the control module responsible for the rear cabin light system is not working correctly. They told me that replacing this module will cost me around 1000, including labour. This is a bit pricy for a few cabin lights, so I'd like to know if this is a known problem or if there is any way I could poke at some wires or whatever myself in an attempt to fix this without having to sponsor my local service center. The cabin lights in the front, including the sliding roof controls, work perfectly. It's only the ones in the back which have the problem.