I believe you have to pop the whole assembly from the visor with a wide blade or finger tips to both sides and bottom middle. Not done it myself yet but need to!
The whole unit changed for a 2nd hand one, the switch was broken. The passenger side lights on the sun visor work fine, I didn't realise you need the ignition on for it to work!
I have the full books workshop manual and I have a shortened version on a CD, if you need that it is on my "skydrive" which I can send you a link to if you PM me your email..!!