How's things Gar.
I have experience with changing the above on hondas. Very easy to do (10-20min). I just did a little read about the m54 box and it seems to be the same theory as the H box.

Not m54 box but similar.
Where 14,15,16 bolts onto the box will be the similar to yours.
http://www.estore-central.com/bmw-parts-catalog/E46-M3-S54/Coupe/Manual-Transmission/S6s420g-Inner-Gear-Shifting-Parts/