No need to backup the firmware as such, versions are freely available anyway. More important to back up [Only registered and activated users can see links. ] and your unit's internal file system fully. If you just want to preserve and restore your 'favorites' following a reset, restore the current.gpx in Garmin/GPX folder.

I have 3 units with US/NA LM. nuvi 40, 1450 and 3597. I don't bother updating them all the time but easily can if you require a unit running the current map. Also have a a few 310 and 6x0 and one 765 NA model but they're not LM [not a problem anyway of course] Can also run any of my other AU/EU units with a US map. If it's not going to be too time consuming let me know what you want tested. I would make the point though that you only need to place the portion required or the entire US or NA map on an SD card [x:/Garmin/gmapsupp.img] to use it. Use a minimum 4GB card and there's no problem at all to fit all US/CA/MX.

PS: Native Texans with a self-depreciating sense of 'humor' are rare imo. Were you born in a Northern State? Notice i left the 'u' our of favourites and humour. I did that just to humour you ... sorry, humor you.