That actually sounds amazingly complete. You may need some miscellaneous screws and stuff. And there are actually two wiring harnesses (but you may have both). One is the main harness that runs from the trunk to the dash and carries the video signals up and the radio hook-ups back to the trunk. The other is a short adapter lead that just connects the main harness to the nav computer. You may also need the nav computer mounting bracket and trim piece.
I do not know of a way to hook up XM so that it integrates with the monitor display, but BMW's Sirius will connect. If your BM53 radio module is new enough, it will support Sirius. Then, you just need to add the Sirius receiver module, an Sirius antenna, and the Sirius-to-CD adapter cable.
To get aux video, you will need either the BMW TV/Video module, or one of the aftermarket video input modules like the Deitz or the one that EIS sells.
Also, you may want to get the Aux input adapter for the radio, since your radio will probably support it and it is easy to do now, during the main install.
Here's a great detailed X5 retrofit post to study.
http://www.xoutpost.com/articles/all-...system-x5.html