I have an '02 X5 3.0 with factory navigation (Mk3). I believe the vehicle is 11/01 production. The nav is acting a little odd and the dealer said they would replace it and upgrade it to the Mk4 (as I am still under factory warranty). Now the service advisor is saying that the Mk4 will NOT work as the wiring is different or the systems will not communicate and that it has to be the CD-based version. Does this sound correct? They said they emailed BMW. I'm sure I've read about 2002 X5's being upgraded from Mk3 to Mk4 just by swapping the "drive unit". I also spoke to one of the tech's and he wasn't sure. I called another dealer and spoke to their parts department and asked teh same question. They said they couldn't find any documention saying that you could simply pop in a Mk4 drive into a 2002 X5. Maybe it's only for later production 02's or just not a Certified BMW "upgrade".