GPS 4.80

You might be able to do it over WiFi.

I was hoping there was something like the way the device firmware can be updated by downloading a file then copying that to the device.

there is such a way, if somebody provides the right GPS fw file for You, then You should copy it to the RemoteSW folder and it will update itself. (the GC or GCM are doing the same via network)

if i remember good the filename is 006B310706.GCD , i have it , so if You write me a pm i can send it to You

Конечно. Этот файл есть на странице загрузки обновления

If some one pulls the file off their unit and gives it to, but there is no Garmin supplied way.

Place the file in the Garmin\RemoteSW folder

https://forums.garmin.com/cfs-file/__key/communityserver-discussions-components-files/402/006B310706.GCD