Don't even bother with a used barrel.
You are still going to have to have a gunsmith put it on just like a new barrel. Things he will have to do are...........Remove the old barrel, face off the receiver to get a truely flat face to torque on the barrel, face off the torque shoulder so that the sights and writing line up where they are suppoose to, Face off the breech to provide clearance for the bolt face, reream the chamber to achieve proper headspace, repolish the chamber. The only thing that he won't have to do is thread and crown the barrel. But I doubt that would save you any money there.
After he does all of this you will be left with less threads than what would be on a factory barrel. It probably would not effect any safe operation but I like to have all of my threads there to hold the barrel to the receiver.
You may as well fork out the money for a new barrel.
Go to
http://www.midwayusa.com/rewriteaproduct/697469 and you can get a new Adams & Bennett barrel for $90.00. I don't know how good they are but here they are. For about $150.00 you can get a Montana barrel
http://montanarifleman.com/barrelpricing.htm which are probably quite a bit better than A&B.