Idk, I DIY swapped out old gas water heater for an electric heat pump water heater heater and it was super straight forward. If you have the plumbing and electrical skills to add a circuit and move your hookups (since on most gas water heaters they are on top and most heat pump water heaters they are on the sides top and bottom), you probably have the skills to safely disconnect and cap off the old gas line. Just be sure to use pipe dope that is rated for gas, and check with soapy water once you pressurize the line again for leaks.