I have a print by JJ Audubon (1785-1851) Passinger Pigeon?

My husband has own this print for 25 + years and was thinking of selling it at a yard sale. Before doing so I did a bit of research and have found this print, exactly the same as mentioned in the Audubon Galleries Origional to possibly be worth $ 29,000.00. how can I have this determined and appraised.