Congrats on the car!
TBH just use a USB drive for music, also much easier to put music in with drag & drop (I hate iTunes). Unless you're a mac person.
I used to really want to retrofit an iDrive when I first got the car but then played around with it in other cars and was kinda "meh".
There is a "retrofit kit" being available (
http://www.bimmerretrofit.com/portal.../brc01p10.html) but you will need to ship it over (just the parts will cost $2,000 to $3,000 plus shipping) plus install costs you're looking at around $5,000.00.
OR you could try an aftermarket option:
http://www.1addicts.com/forums/showthread.php?t=760484