
Will these watches be functional once I change the batteries, or will the batteries having been left in the watch for that long a time ruined the watches?
The only way to tell is to open them up remove the old batteries and give them a try with new ones. If the batteries have leaked then there is every possibility there will be corrosion to the inside of the watch, sometimes the batteries leak sometimes they don't, it's pot luck I'm afraid. Although I would be quite optimistic, the watches are relatively modern (dating from 1995) and the batteries where quite reliable in the 90s.