on the right side, just above the step towards the rear is a lever. This is the traction disconnect. Flip that to the opposite side it's on now, and it should roll. by the sounds you're saying it's making, it either stripped the splines out of the torque limiting clutch (most likely), busted the center out of the torque limiting clutch, or stripped a good portion of the splines off the input shaft in the transmission (most costly). I'd say very small chance of it being the output from the transmission to the rear end. No real good ways to open things up and look shy of unbolting front from the back and rolling them apart...might be able to pull the hydraulic pump off the top left front corner of the bell housing...but I don't recall if you can see past the ring gear to see the clutch spin.
The shaft new is almost impossible to find, and I think requires a 2x split, ahead and behind the transmission. The clutch can be fixed by a single split ahead of the transmission. Will cost you probably no more than $1000-1200 for repair, most of that in labor to split the tractor. I have 2...put new clutches in both. The splines on the input shafts are worn about 1/2 way through, but due to cost, and I don't use them heavy, just put new clutches in them and may rebuild later if they go again.
3 point should still work, remote valve should work, but it won't move. Those normally have a bit of a while of the fluid...you probably won't hear that at all if it's the clutch. No spin, no pressure, no fluid moving=transmission locked in park
