If you are talking about the New Model Army .44 caliber, they are not that "special"; there were a hundred fifty thousand made and any fair size gun show will have a half dozen or so.
Assuming your "guesstimate" of condition is close, around $2000 would be a good price. As to selling, you can try any of the on-line auction or sales sites, like Auction Arms or Gunbroker. Or you can try a gun show, but I can pretty well tell you that is not the place to get the best price, since a buyer will likely be a dealer and will want to buy as cheaply as possible.
Another possibility is to put it on consignment at a local gun store or antique shop. (It is an antique, so it is a "non-gun" as far as Federal gun laws are concerned. Check state or local laws, though.)
Jim
