I cannot recommend replacing the gate of a gate valve. I would recommend replacing the whole valve with a newer ball valve. Gate valves are designed to be opened and closed very infrequently (as a opposed to globe valves, which are designed with replaceable gaskets). The advantage of a gate valve over a globe valve is that the former is “full bore” when open. Gate valves are not usually used as shut-off valves to fixtures. Except for pipes greater than 1″, ball valves are better than gate valves. Except for these larger supply lines, I have stopped using gate valves.
NtP