Assuming it's in decent shape, your gun is worth at least twice what you paid for it. Your buddy gave you a screaming deal. Go to a gun shop and see what $150 gets you in a handgun. It definitely won't be a Ruger Blackhawk.
If your gun is an old model, it is worth 3x - 4x what you paid, depending on condition.
Now..... Let's see a picture!
Rob