For the tailights to LED's there are numerous discussions related to what programming / other would be involved relating to the E46. I don't think that X3 would be that different. For E46 info related to LED tails check out E46Fanatics.

I recently was an Intel conference sponsored by BMW and there was a variety of X3's (colors and styles). I noticed that the X3 angel eyes really made a difference in the front end appearance of the X3.

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E83 - Aero PKG Mods installed: Homelink mirror. CIS-IBUS video module, AUX, Rr Dr Release, stock wheels, Remote start, CarPC (Atom) & mud flaps - NAV - MKIV - NA Map DVD - 2011
E46 - 18.5 wheels/tires (summer), 17 stock (winter), Homelink, NAV software upgrade, BMW video module, Radio to V53, AUX, USB IBUS interface,BMW alarm install, CarPC(Epia), remote starter, tank battery & angel eyes. NAV - MKIII - NA Map CD - High Version 2008.1