There was a number of threads on the Assist recall on another board - although they didn't indicate that the TCU always had to be replaced (depended on which network the unit was using). Bascially for some 2006 X3's the TCU would deactivate itself because of an issue with the TCU's Mobile Identification Number.

Here's the link to the thread with the text of the bulletin:
http://www.bimmerfest.com/forums/sho...d.php?t=154301

As for the list of programmable options for the X3, they are included in the manual.

Cheers,

Pierre