If only it were that easy. Finally got the service manuals back from my brother, and now I see what I didn't before.
I do have to take the sump off. What I had thought was the chain adjustment cap screw was just a cap screw holding the sump on. The adjustment screw is behind the sump, and to do it the way I thought to I still need to take out the adjustment screw.
On the older models you can slide the sump out and leave the PTO shaft in place, but on live PTO models like this one, the shaft has to come out with the sump. That means I have to work through a hand hole around the clutch to get to a snap ring and remove it, and take the top cover off to drive the PTO drive gear and bearing off as it's removed. And then there's removing the hydraulic pump and the hoses and cylinder for the Eagle Hitch.
And there's no big nut on the axle, according to the book. The sprocket is held on with a snap ring. If there's room to work, I may be able to remove that snap ring and slide the axle and bearings out of the housing. I'm hoping, anyway.
But no matter if that works or not, this whole repair is turning into one big PITA.