I always google the guy's name, phone number and address before I send money. I learned the hard way. Even talked to the guy. A simple search after he burned me showed bad results. Not the same guy as yours, though.
22 Diamondbacks are very desirable. As with many collectible and desirable guns, the blue book does not reflect current market prices. Many guns on there go for much more than they are valued at. I could make a living buying guns at their blue book prices and selling them for real market value...
The blue book doesn't count when something is very disireable, as diamondbacks are. The best thing to do is sell it on auction. It will bring the current market value. Do it before the end of March, though. Traffic and prices go down after that.