Why even bother with "official" update?? You and we are here to make things easier and cheaper..What you'll need to do is to change current iGO software which is (I believe) on your SD card, with the crack*d iGO version. After that you can easily add newer maps, pois and other content without naviextras..Just copy/paste. Simple as that.
But first of all you'll need to check whether iGO app is on SD card or on the internal storage. That is crucial info for the next steps. You can also make some screen shots of the SD card folder/files structure.