I am looking at same issue. Much depends on status of the core. If dry and intact then one can fill in screw holes with exoxy, and then put more glass on top. At that point there are several options I have not chosen one yet = cheapest is probably more glass with sand as non-skid. Treadmaster is a possibility though some are dead set against it. Molded glass nonskid is another route though think requires professional know how to carry it off.
If core is a problem then it becomes more involved. I am going to cross my fingers on that one though believe core is good.