I installed an Xtrons into one of my X5 with NAV. Unless your car's wiring was cut previously it should be a plug and play installation with the long (patch) cable going from back to the front - quite a bit of fiddling to get it concealed properly..remove a lot of trim and front passenger seat. Just string the long cable over the seats to test first.

Look at the wiring diagrams if you want to, but I wouldn't do anything until you get that patch cable.