After doing an OEM MKIV Navigation system retrofit in my wife's e46 a few months ago, I decided that I really wanted to do the same in my X3. I love the integration of phone, navigation, Sirius, reverse camera and iPod via the Intravee II.

Anyhow, I ordered up all the parts for the X3 retrofit from an eBay seller in Germany and had everything shipped to me here last month. I got around to tackling it finally with my friend Andy, who is a BMW Master Tech...

Link to all the part #'s on Realoem.com. The wiring harness is part # 61120390114 if you are piecing the parts together yourself...
http://www.realoem.com/bmw/showparts...65&fg=95&hl=40

First, here are the OEM install instructions:
http://www.bigpatsfans.com/x3_oem_nav_retrofit.pdf

All the parts. You don't need part "O" for USA cars (all are pre-wired for CD changer)



The wiring harness layout:



Basic map of where things will go in car:



Start with the wiring harness in the trunk. These 2 cables will connect to the back of the MKIV. The GPS antenna is here also. The instructions call to route the GPS antenna to be behind the instrument cluster. Not sure if you could tap into the shark fin.





Pop the rear seat off and the bolster behind the driver's side back seat. Everything just pops right off.


Route the wiring harness down the bolster and tuck it along the existing cables. Secure it with zip ties.



We then removed the driver's front seat and the center console. The wiring harness runs along the floor to the front of the front seat, across the floor and up through the center console to behind the radio.



Remove the sunglass tray, the AC vents and the old radio. Everything essentially pops out and is secured in by Philips head screws.






Removing the armrest provides better access to the carpet, which is very stiff:


The harness routed up through the console area:


The wires plug into the existing connectors for the old radio:


You need to remove the instrument cluster. You'll tap into the vehicle's speed sensor coming out of the wires behind the cluster.


While we had the cluster out, we removed the seat belt speaker chime. It just pops right off with gentle twisting:





Connections made to the fuse box:





Putting everything back together:






In the trunk, I attached the bracket for the MKIV drive, Turns out I need to order a different bracket that supports Sirius too. I just stuffed everything in there for now. I also connected my Intravee II and iPod now:


The part # of the bracket I need to order, that hold the MKIV drive and the Sirius unit: 65503411774
RealOEM.com BMW E83 X3 3.0i Bracket, satellite- radio

The last surprise was that the carpet piece for cars without Nav is different than the carpet piece for cars with Nav. My existing trim piece was too deep. I looked it up, and sure enough, I need this $100ish part: 51473412225
RealOEM.com BMW E83 X3 3.0i LATERAL TRUNK FLOOR TRIM PANEL