Sight unseen, and not knowing local regulations, it's hard to give an answer. What I can do, is give you some reassurance that your water protection does not vanish when a check valve in an RPZ fails a test. The RPZ provides three levels of protection. The check valves are levels one and three. Level two is the relief valve, and as long as it works, the water supply is protected.
All that said, the RPZ should not be dripping any water from the relief valve when the system is idle (a squirt of water when a zone shuts off is permissible)
If you know what you're doing, it's always cheaper to repair an RPZ than to buy a new one. That's a big if, however. A full set of repair parts for a one-inch Febco 860 RPZ could run you over a hundred dollars.