I don't know how the trim panels are removed but I can point you to diagrams showing an exploded view of the components. These diagrams can be found under General Info & Guides, 28 BMW Online Parts Catalogue. The diagrams of interest appear to be these:
http://www.realoem.com/bmw/showparts...33&hg=51&fg=45

and
http://www.realoem.com/bmw/showparts...25&hg=51&fg=50

Please let us know how you do it if you do manage to remove the trim.

Simon