I got a phone call today from Garmin; "we can't mend it ... ".
This begs the question, "what is wrong with it?". Legally speaking, Garmin may not be on the hook, but certainly I think that you are entitled to an explanation as to why the unit spontaneously failed and is considered irrepairably damaged by the manufacturer. Assuming that you didn't abuse it in some way, then either this particular unit had a unique manufacturing defect (in which case Garmin should replace it, warranty expiry or not), or there is a generic defect in the product (which sounds unlikely, and if true I and others on this forum will want to hear all about it).
My advice is do
not be hostile or argumentative (since if you do they may well just tell you to
off), but by all means keep up a gentle but determined pressure. If the person that you are speaking with can't or won't help you, ask to speak to their supervisor, and push it up the chain until you get a result that you can live with.