I wouldn't pay more than $200 for it, considering that you can buy a new one for $350.
Proper way to carry it? Well, I would have a round in the chamber, with the hammer down. Same way I would carry any traditional DA/SA gun. I only keep such a gun cocked for carry if it has a frame mounted safety - such as the HKUSP. Then U could keep the gun cocked and the safety on.