I believe the units are identical but not really sure. About 'reflashing', that's just software that needs to be loaded and you can do this yourself. I suggest that you research a little bit more on www.x5world.com, a lot of information re navi, BT, etc... good luck :cheers:
Regardless of what you get, btw, I HIGHLY recommend the KrisL modified V29 firmware. It gives you a nice mountain scene as your background in perspective mode and makes the text a bit more user friendly.
the Land Rover nav computers that are compatible with the M5 are not MKIV but MKIII, which is the same as 01, 02 M5. You can not change the firmware with current hacking tools, but with a hacked software cd you can change the logo to ===BMW=== But will still have the Land rover User interface wich is old 2001 software and sucks. It was never updated even in the 04 Range Rover. And Kris Linquist firmware load will not load on it either.
Do a Google search for BMW MKIV navigation. There are places out there to get them. I would recommend buying from experts (forum members, bimmernav, ect) instead of off ebay or something