Sat/Nav - yes, you can pick up a MkIV and just plug it into the existing wiring harness and you should be up and running. Make sure the MkIV is for an i-bus vehicle that has a color screen.
Like the Sat/Nav, the 6-disk CD changer is also a simple plug-n-play install. Look in the Stereo section of the home page for DIY instructions -
http://www.xoutpost.com/articles/x5/s...er-bmw-x5.html
Regarding the phone, look into retrofitting the BMW Bluetooth phone system. Lots of info at
http://www.xoutpost.com/bluetooth.php