I have done the NAV retrofit in my X5 and 540, as well as two other friend's cars. While it wasn't in an /06 model, there is nothing different about the install. First off, the dealer is the wrong place to get any info on this. They will tell you it is not possible. I am not at all fond of any aftermarket units that you will probably have to mount on the dash or on a goose neck. Nothing beats the clean look of the factory NAV and you open up several other options like Sirius radio with on screen display, TV, DVD, Backup Cam, etc. you can buy all the parts new for $3500-$4000 if you're willing to spend that. You need much more than just a wiring harness. Otherwise look for some used deals. If you can install car stereos etc. you can do the NAV retrofit. If that's a bit of a challenge, then I suggest you find someone that has done it.Unfortunately I'm in Canada!