According to Ruger's site you can buy a barrel for as little as $120.00. They unscrew and would need the cylinder gap set when reinstalling. I'd let a gunsmith do this one. While you are at it, have the forcing cone redone and maybe the barrel recrowned. Heck, with that much barrel ,just take it to a gunsmith and tell him what you want done. It might not be much more than buying another barrel.
HWD
HWD