Greetings Ronald:
The best way for you to sell your black walnut trees is to "market" them via the advice and assistance of a professionally trained forester.
Seeing that you reside in New York, I suggest you first start with the New York Dept. of Environmental Conservation:
http://www.dec.ny.gov/lands/4972.html
Ask your local state forester for timber marketing assistance. Please note, your local state forester may refer you to a professional consulting forester.
Best of luck!