Hi,

Quote:
Can I open the valve up to clean or service it or would the entire valve need to be replaced?


If available, replacement.

Quote:
I own a circa 1980 Hardwick gas range


Model#?

Quote:
I have been advised that the parts for this old stove are not available. What other options are there besides a new stove?


Sending them away to a company that can rebuild them...
www.erepco.com/
Self-proclaimed "world leaders in the remanufacturing of thermostats, safeties, flame switches and gas valves for the aftermarket appliance industry".