Garmin GPS Updating
I did this in Windows because well...just because. I installed the Garmin USB Drivers and connected the device to the system. The Garmin device showed up as a drive on my computer. The garmin drains the batt I think but as long as it is plugged into the computer it is powered.
I did not want to put a dam SD card into the device so I deleted gmapbmap.img and gmapprom.img out of .System\Garmin (If I remember. I know it is in .System) The bmap.img was 50mb and the prom.img was 1gb. I backed them up before I deleted them. MapSource would load the device then.
Any unofficial map release should have some install.gmap.exe which will work with the maps in a folder in the same dir with a dir with the extention .gmap. It will unlock the maps copy them to your system and opens them up in a special MapSource to load them into the device.
Their is a util to unlock the maps not by garmin. Their is a util to load the maps by garmin.