The valve that replaces the Rainjet Classic is fairly inexpensive. I suggest you replace the entire valve.
With that said, I've repaired many Rainjet valves myself for various reasons.
It depends on what the bonnet of your valve looks like. I don't remember if the older 711 style Rainjet said Classic on it or not.
Does the top of the valve look like
Click on me
or does it look like this.
Click
Pick one and I can tell you exactly what to do.