Options for fixing depend on what's broken. Usually single keys can be fixed rather easily, depending on your mechanical skills. If whole rows/columns fail it's a contact problem with the membrane, tracks on the membrane eaten away or something similar. A single key must be a problem of the membrane contacts or a mechanical problem, possibly just dirt.
Remapping should be pretty easy, there are plenty of
keymap editors on Aminet. In hardware banging games this won't work, however.
