The current barrel on my Rem. mdl 12 (round barrel) has a poor bore. Rifling is present but clearly the early corrosive rimfire ammo has taken its toll. I had planned to reline the barrel at some point (which is easily a $200 job it seems) but I may have a line on a good replacement barrel. What is involved in replacing the barrel, and what sort of cost would be involved? I'm guessing this isn't something I can do at home.