I have a 2002 E46 M3 with 178K miles. The navigation system now does not work. Does anyone have any suggestions where I can get a relatively inexpensive navigation system for my car, and how hard it is to replace the system by myself. Also, can I use a DVD system instead of my CD system, and where could I purchase same. I would love to have a working navigation system again since I would like to keep my car for at least 225K miles.