Kevin -- Well, it depends on the quality (i.e., grade) and accessibility of these three trees. However, there is a very good chance it will cost you to have these three trees removed from your yard!
The only accurate way to assess the value of individual black walnut trees is to contact a trusted forester or timber buyer for an on-site assessment or valuation.
Therefore, please contact your local Michigan Dept. of Natural Resources service forester for a list of local professional consulting foresters and/or a list of local licensed timber buyers: