There's always the slight chance that the problem is due to a hardware component of the PCB although the vast majority of such failures involving USB connection (data transfer, changing or both) are due to the physical connections from the socket to the board itself. Despite your reluctance, if you have any soldering experience at all and only a cheap soldering iron it's not a big job to re-flow the connections. The main issue for novices is not using enough flux which results in bridged connections.

If you decide not to "start waving a soldering iron about" (don't point that thing at me, lol) then the device can be successfully updated from the media card using text commands. It's possible to delete, overwrite or add files and entire folders from the card that way. Read this thread: [Only registered and activated users can see links. ]. You can obtain all updates such as lifetime maps and other ancillary files using a 'clone' of your nuvi. Make a copy of it's GarminDevice.xml and put it in a folder named GARMIN on an otherwise empty USB stick then GarminExpress will update it, just as if would the device itself. You can then transfer the files to the device using the txt commands from an inserted microSD card. If you need further help with any of that post again here or in that thread.