69 weird brakes

So I hopped in my Dart to give it a winter warm up and a really strange thing happened. First of all the motor was running at a much higher rpm than normal, by about 400 rpm. Wouldn't drop down even when it came up to temp. Then whenever I stepped on the brakes, the RPM went up about another 200 RPM. So I'm thinkin vacuum leak, probably on the brake booster. I've never had this happen before. So I went to Rock Auto to see about a replacement part and although they list it, its out of stock and I know what that usually means. So anybody know if they can be rebuilt or if theres an alternative source for another booster? I guess 50 years isn't a bad lifespan for the first one! Thanks in advance.