If you get the IT manual they show this set up. If I am not mistaken you can remove the 4 bolts that hold it in (drain the rear end first and I think the hydraulic reservor also) and the whole assembly should slide out, it will be with the shaft like 3 feet long. The housing with the four bolts is where the snap ring is but you have to take it out and apart to service it. I think altho it been a long time that housing has a seal, a bearing and the snap ring and in order to get to the seal you have to remove the other two. The IT manual has some real good directions on how to get it out and apart, they have them at tractor supply can't remember the #.
Now the bad news! When I did my 841 (ealier version of yours) I couldn,t get it out I had to remove the hydraulic cover to get at the couplier that is at the rear of the transmission. Somehow the front of the shaft got peened over and it wouldn't slide out of the couplier I had to go in with a real small file and clean the end up inorder to get it out. There was a lot more to it but that is the basic's, need less to say it made a short duration project into a major time consuming pain in the back side.