Hi,
my parts catalogue still indicates that a remanufactured radio/cassette is still available for your vehicle but are very expensive (your dealer will advise you on this as it varies from location to location). If you were to fit an alternative you would need an adapter cable between your head unit and CD changer wiring loom, which would be available from any decent car stereo store relatively cheaply. Or, another option is to contact a local breakers yard and source one which would probably be the cheapest option.
Rich.
How did you get on?
BMW Technician
5 years main dealer experience.