I removed my 6 disc multichanger and replaced it with the BMW ipod adapter. I thought i would have to recode but it worked straight off (but my car was already mp3 enabled). Make sure you get the latest ipod retrofit kit from BMW as there are a few older versions kicking about (the newest ones work with iphone 3gs and i've been told 4).
I coded my V.O in both ecu's (CAS and LCM) anyway as i want it 'just right'. To add +IPOD to the V.O you must first remove $672 (cd changer fitted), otherwise NCS just gives an error.
Using NCS is not too hard, you just need to read up/research before attempting anything.

Gav