Nav runs off the SD card, to change the program you just need to change what is on the card (they are available all over the internet)
I should point out now that the Dynavin is not new, Us E46 guys have had it for over a year....The new E90 unit is identical to the existing E46 and E39 units, it just has a different face to fit the E9X cars.
There are literally hundreds of pages of info available, start here:
http://forum.e46fanatics.com/showthread.php?t=793437