The way BMW Instructs us to do it is as follows...
1. Remove Glovebox
2. Remove lower trim panel
3. Remove air duct by unclipping it and take it out
4. remove screws and til controll module housing down
5. turn the lock to unlock it and remove the cover
6. pull microfilter out
in reality at most dealerships we;
1. brake the microfilter at the 'brake points' (but not all the way thru) so that it is flexable/foldable
2. pull carpet down and wedge it under something out of your way
3. unclip air duct and push it out of the way
4. unlock box from side and open.
5. replace microfilter...
and as a tip, put something down or pull the floor mat back befor you remove the old micro, it could get stuff everywhere