its a PITA to replace the wheel... one of the first things i tried to do when i got the car was put a MOMO on. firstly you're right, you'll need a DRBIII to reset the airbag light, but it'll come back on once the system realizes there's still no airbag, but i also found out some more pieces of info...

there is a steering wheel angle sensor that is used for both braking assist (BAS) and traction control (ESP). remove the steering wheel and these features are useless. i cant remember if it affects ABS or not.

the steering wheel hub needed to convert to a MOMO is super hard to find. there is a generic Mercedes adapter (6004, IIRC) but it needs to be drilled out to fit correctly.

just FYI --