Never have done it, but I would start by removing the light lens from the light bucket (flat-blade screwdriver, pry out), more than likely there are screws hidden therein, and then unsnap from the inner mounting...? :huh:
Ok - so this is in the service manual (haven't done it myself)
First, remove the lens as mentioned above, then slide the vent to closed and you will see a screw inside the vent - remove that. then there is a screw near where the light is and on the left rear assembly, there will be a nut, too. Once you have those removed you pull the assembly out, there will be a single plastic clip on the grille end of the assembly (as opposed to the light end) - once you pull it out, there is a connector for the map light you need to undo, then you can have your way with it!