I have an early Craftsman RAS (with the digital readouts) which has not let me down... ever. I don't know if it is the same saw as your model, but I wouldn't be concerned about reliability, although you should have the owner demo it before you deal. As for price, that's subjective, since there aren't that many RAS's floating around to establish a reference. I'd suggest you consider how much you need it vs. how much you can afford vs. cost for a similar new unit, and haggle from there. It never hurts to walk away if the price seems too high. This way, you give the owner a chance to come down, and you can always change your mind if he doesn't.
...eight, nine, TEN! Yep! Still got all my fingers!