These electronic things are so expensive to repair that even if you could get it repaired for free, it is outdated and without all the new features. So, if it were me, I'd buy a new Garmin. Costco had the best price the last time I bought one. (Actually, bought three, two for each of our kids and one for ourselves.)
I like your "save the radiator cap" comment.
Holiday Rambler Navigator DP, Hummer, and Honda VT1100C Shadow