The site hasn't uploaded your latest comment, so, there generally 2 types of gate valves, one with a screw/shaft that operate a gate, and commonly used on water mains, and another that has rubber washer on the end of a screw-shaft, generally used on boilers, which may be your model. If the latter, there may be parts available.
The usual is to upgrade to a full-port ball valve, as well as replacing the water main, from the street main to the house. this usually involves "L" or "K" copper or schedule 80 plastic, which because you will be adding ground rods at you're elec. service, that requirement will be met.