Take it slow. My BT upgrade on my E46 was an endeavor by itself. It was a retrofit using the existing Motorola prewire for CDMA telephone. I never cut any holes for the pairing switch in the center console and just left it loose underneath the cup holders. Once installed VR works with both NAV and BT. I've set it up but use rarely use the VR part of it. The OS upgrade another endeavor was easy in that I only added a new start up screen and just a few graphics. This was with a MKIII. On the E83 the OS upgrade was for the dual layer DVD, startup screen and some graphics. Even having someone around while doing this for the first time will provide a confidence builder. Personally the time delays while watching blank screens made me nervous a bit but all I had to do was wait. One endeavor a few years back was to install a TV module. The first one I purchased was an older style with its own NAV CPU. It was kind of weird to see two different computer views. Later updated with a more current TV module and all went well.

I guess just be patient and do a little bit at a time. More time consuming is to install angel eyes on the E46 or LED tails.

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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