The barrel is screwed into the cylinder, but normally they're firmly glued or loctited in place, and it takes considerable heat to break the bond and unscrew it. I know the Geordie collector on youtube unscrews his but none of mine have ever been like that.

The bull barrel gives very good balance and they can be made to shoot very nicely, but a lot of them are dogs. The trigger's shortcomings are well documented, you can polish the sear/trigger interface and fit a lighter spring, but it'll never be a match trigger. Perfect alignment of the loading tap is critical, if it's good they can be very accurate, if it's bad it'll do your head in as the pellets go all over the place.

Value is all about how much somebody wants one, and you see them advertised for silly money. If it's really good with the full set of sights then maybe £250 or a bit more, but you're into the price range where there are arguably better choices so the market is limited to diehard fans.