Overall for the cost of what a new kart barrel and bushing and having it fitted, is not worth it, unless you could get a good deal from someone knowledgeable like 1911 tuner.
Most smith's don't do barrel fitting and finding one locally, that you can trust or that will do the work reasonalbly priced is difficult to do.
Your going to have to put at least another $300-$350 into the gun and even after you finish it. The gun will still only be worth $400-$450.
Just sell the gun locally on the backpage.com they have a good sporting good section that allows guns to be sold for free.
You should be able to get $350-$400 for the gun and take the money you get and buy a SA range officer for $750 or even a RIA tacticle for around $500, would be better than sinking any more money into the norinco.
Treat the small amount of money you lost, as a lesson , and don't buy any low end guns used anymore, if you buy used stick with the top names and you usually don't have any issues, like colt , remington, ruger, mossberg, SA, kimber etc.