If this were mine and I wanted to do an inexpensive "Restoration" I'd do the following:
Disassemble the gun into it's main components. I.E. Remove the ramrod and take off the barrels by pushing out the wedge thru the forend. You can also remove the locks and trigger guard if you feel competent to do so.
I would then get a can of Restore a Finish in Walnut and go over the stock lightly. I would also wax the metal parts with a good quality paste wax which will clean the metal in the process without removing the patina. This process shouldn't cost more than $10 will improve the appearance and with a little elbow grease and you now have a family heirloom to hang over the mantel.
Others may have additional inexpensive ideas for you to try.
Jim
