Wow how unfortunate. While it sucks, it sounds like it may have been accidental, and you may not know what kind of day the movers were having or what is going on in their personal lives. I am not making excuses just that I would want to make things right and move on. I think what I would do is call two known pinball repair/restoration guys that could possibly give you an estimate to replace the cabinet(with decals) and swap everything out properly. I would get this estimate in writing so you have something to present to the moving company and or small claims court(worse case scenario) to settle a claim.
You sound like a mechanically savvy guy, so I would say do not mess around trying to glue your fathers pride and joy-do it the right way and replace the cabinet,etc. You could purchase a cabinet and decals and with the help of Pinsiders here-you could do it yourself? Or you could find someone locally that could probably help you out-lots of pinheads near you. You have come to the right place, Pinside and Pinsiders are always willing to help with problems. Good luck with whatever you decide to do.