I've repaired my screen in the past. If I lose a button I will probably just upgrade to a newer model rather than put more money into my old 450.
That is what I looked at doing... until I checked out the price and the specs of what they currently offer. Garmin has done little to really improve the products and yet the prices are even more insane than ever, AND they removed the physical/tactile buttons. $900??? Are they out of their minds? And that DOES NOT INCLUDE their stupid "subscription service" to get traffic info. I bet it still can't even play music when running on battery (yep, that is standard for the Zumos). My conclusion was to just repair the 450 again (which, thankfully, is cheap and fast) and wait/experiment....
In the meantime, I am also going to experiment with using a smartphone and sewing touch-screen thread on the tips of the gloves' index finger and thumb. I am tired of being a prisoner to the Gamin products. Phones have their own issues (not rugged nor waterproof, often data-dependent, lack of physical buttons, conductive screens, not terribly bright, etc), but at least they are something I will already have spent money on, I can load any app I want, get regular updates, and have TONS more possible functionality. The phone "X" mount and conductive thread arrived several weeks ago, I just haven't done anything with it yet.