Order a couple pads from here and clean the metal with oil

http://www.exploreproducts.com/big45-frontier-gun-cleaner.htm

use a piece of a frontier pad on a cleaning rod to get some dirt out of the insides of the barrels - then get a good coat of oil in there to slow the rust.

clean the wood with a furniture cleaner then put a thin coat of paste wax on-

hang it on the wall with the hammer showing and you won't need to hunt for a replacement one.

10- 20 bucks total cleaning supplies and you have a piece of family history on the wall