It depends on the merchantability and quality of these two black walnut trees! However, homeowners should never expect to sell their yard trees because the cost of removing a yard tree almost always exceeds the value of the tree as a potential sawlog!
My advice: Contact a local NJ Forest Service employee for a list of custom sawmill owners and see if any of them also happen to be certified arborists!
NJ Forest Service: http://www.state.nj.us/dep/parksandforests/forest/community/index.html