Gas valves are generally Metal to Metal spring loaded tapered valves. You should be able to remove the plug of the valve and lube it. Off hand i do not know what to use as the lube so I would contact someone that works with gas and ask.
WBCCI 12156 AIR 3144 WACHUNG TAC NJ6
2004 Excursion 4x4
1991 34 ft. Excella +220,000 miles, new laminated flooring, new upholstery, new 3200 lbs axles