Value wise, it isn't worth re-bluing. Considering the condition of the barrel as you describe it, a re-blue will improve it's value. But to a limit since it will no longer be original. In it's current condition, it will never be collectable. An alternative is seeking out a new barrel. They can be had for less than $100.00. Numrich Arms has them from time to time and I'm sure you can find one on the net somewhere.
I just wanted to add,
A few years ago, I picked up a 99% condition Model B with a 4 inch barrel, in the box with one magazine, a box of 30's era ammo and the original instruction tag. I paid $50.00 for it and sold it for $350.00 to a dealer at a show. The only visible wear was where the saftey had been used. It may have been unfired since the box of ammo was full except for the rounds in the magazine.