This is not totally easy but a "little bit if effort" will have HUGE results that's positive for your grandpa, future of the forest, sale price, etc...
Call the forester for Ringold Co, out of Creston. Have him look at your ground. Randy Goerndt. Get his opinion & also, IMO (my STRONG OPINION), have him walk the land to write up a Timber Stand Improvement Plan (which could also include Weed tree removal plan) that you also should do after possible logging to make the timber better for generations.
He will give you opinions on logging potential and also would have the list of good buyers that you want to BID on the trees. No way, no how, would I listen to one bid only and get talked into it. I've seen log BIDS, on walnuts for example, have 10 bids in response, almost every single case, the spread is staggering.... For example, I marked my own sale and sent it out for bid about 5-ish years ago on a very conservative, large tree & trees that "needed to come out".... I think this one was maybe 125 trees on one tract of ground - about 150 miles from you I'd guess. These were conservative & ideal trees to remove (did TSI later & kept the best veneer walnuts under 26").... Of about 10-ish bids??..... the lowest was something like $11,000. The highest was like $45,000. Everything in between. Incredible difference. Most sales are like this to some extent. GET BIDS!!!!!!!!!! Make competition work!!!!!
Now, if you know trees, you could do this with help of state forester. BUT.... I'd then likely get a private consultant to help you market your sale, manage your contract (write one), send out bids, etc, etc. Ask Randy who is good private consultants possibly. Make sure you do TSI when you're done so you clean up the junk for making the forest infinitely better for generations to come. Good luck!