Just delete the old paired phones and all the data is deleted. All of that is stored on the combox. When the phone is highlighted, move the idrive knob right and there is an option to delete. The idrive/CIC may have music stored on the hard drive. You can easily delete that. That is all I can think of at the user level.
To update maps see this thread
https://www.e90post.com/forums/showthread.php?t=1461515