"...Depends on the outside diameter of the muzzle..." Depends on the thickness of the steel that is left. Shouldn't be a problem though. It may require shortening the barrel a bit.
The cost of another barrel varies by the type and length. Goble's, here in London, lists 12 ga., 26", 28" and 30" Remington standard contour barrels with Remchokes for $275.50. The choke tubes run between $20.95 each for M, IC, Skeet and Improved Skeet. A Full choke tube runs $36.19. All Steel or Lead in 12 ga. $62.95 for an extended rifled choke.