Greetings Tyler:
You definitely want to contact an unbiased, third-party professional to assist you in determining the fair market value of these trees. In other words, you need to contact and hire an independent, professional consulting forester to assist you in marketing and selling a portion of your merchantable timber to the highest bidder.
Directory of Illinois Professional Consulting Foresters:
http://web.extension.illinois.edu/forestry/pdf/tfb-nres-202.pdf