i did this the other week
On my 2007 E92 335d it was a straight swap
Just remover the 3 screws holding the trim around the air on
use a small posidrive screw driver to relaese the airbag, one spring clip on each side of a/b unit
remove the electrical connector for the air bag
unclip the paddle connector from the MFSW buttons each side then unscrew the paddles
fit the new m3 versions and follow the above guidelines in reverse order
Always a pallbearer never a corpse....