One nice thing about Catalina 30's are that they are like buses, if you miss this one, there will be another one along shortly. I would also worry about the work that's been done. See the boat yourself and check out that hull id number issue. The story about the mast doesn't wash, IMO. That's two strikes. It's way better, IMO, to miss out on a good boat than to buy a bad one. Presume that they are all guilty until proven innocent.
When you see the boat, don't be afraid to poke into all the dark corners. This is a used boat buying guide
I've used and posted before. Some of the Canadian info doesn't apply and the prices are a few years out of date. Check out the inspection link. It's not a substitute for a professional survey, but it will help narrow the field. Bring a scewdriver, take notes and photos. Prepare questions and jot down the answers.
Enjoy the shopping experience.