Firmware for the idrive is separate to the maps.
You need a key to update the maps and the map data.
There is a dealer fee to update the cars firmware (they do all the cars systems) then another fee for the key and another for the maps.
If you wish to risk it there are people on the net that will get you a key at half price then you can download the maps and do it yourself. You must be reasonably technical and put your car on charge while updating as it takes several hours.
Black Sapphire BMW Z4 sDrive35i
Mods: HiFi Tweeters Stubby LED Halos & Front Indicators DVDInMotion SmartTop 313 BMW Performance Alloys LCI Repeaters http://goo.gl/PF4nSz