The cylinder can be saved as long as that's all the pitting there is.
Option one would be to send it to S&W or any really good gun refinisher like Cogan and have them professionally polish the cylinder to remove the pitting.
They could probably get most or all of it off.
Option two is attempt it yourself.
Steel wool would be useless to remove pitting,.
DON'T use steel wool on stainless. Tiny particles of the wool can embed into the softer stainless and will rust later, ruining the surface.
You can start out using a fine cut file to file the surface to get down to the bottom of the pits.
Then switch to some medium to very fine wet or dry type sanding cloth and a wood stick or a wide file.
Wrap strips of the abrasive around the stick or file and use that like a file to finish removing the pitting and to remove any embedded carbon steel file particles.
Use finer and finer abrasive until the area is even and the heavy scratching from the filing and coarse abrasive is off.
Then use Scotchbrite pads to even it up and restore the original factory type grained finish.
Buy Scotchbrite pads at automotive supply houses, where they're sold for u8se in painting cars.
If you need to use a file on stainless, be careful to go over the surface with abrasive cloth to remove all the file particles from the stainless.
Probably, you could send just the cylinder in to S&W and they could save it for a minimal charge.