Dun, i renovated a declinging k-31 fescue field last summer with pretty good results. Grazed it close in June and sprayed roundup. We fortunately had a state program helping with the renovation costs. I let the cows graze the crabgrass that came up and disc once in august and then in Sept, just before planting. What i thought was old fescue coming up turned out to be volunteer ryegrass which is not really a problem here. My cows show a distince preference for the MaxQ over other old fescue pasture. I have to be very careful to keep it from being overgrazed.
I did not do it but it seems to me you could spray in spring, disk,. drill roundup ready soybeans, spray again as needed and let the cows have the beans then no-till new fescue. I would be surprised if you have much old fescue left but i could be wrong.
Edit: We also have a program to put in grass in highly erodible crop land. I once planted beans two years (on old pasture) and got paid nicely to put the pasture back. Beans are nicely priced now.