Agree with Slugo. He might even be generous with its value. Although, it is an A5 and if it works it has to bottom out somewhere in the price market.
Browning still sell parts for these old guns and has a schematic and parts list with prices on their web site. Buy parts directly from Browning since others vendors seem to have significantly higher prices for the same parts.
The Browning web site will also help you date your gun. Your serial number indicates your gun was made by Remington between the years 1940 to 1946. The letter B in the serial number indicates it is a 12 gauge. (the war years when Browning was unable to acquire guns from F.N.)