There's a wing nut behind the lighting rig inside the boot (by the wires leading into the back). It is a bit stiff to pull out and it may seem that there is another screw at the top of the rig but there's not, its just a securing peg and it will pull free with a bit of force. One thats off there's 6 clips around the box. Pop them off and again with some force it will come free.
Matt A, March 2008