I don't know the tractor, so I'm not much help, and what I've got to say isn't good news anyway. First, you really can't do much without a repair manual. Second, is that a lot of transmission work requires major tear downs, and most garage mechanics aren't equipped well enough to do the work.
Not much on my Ford transmission is accessible without a major tear down. I don't have enough equipment nor do I have a shop, so a 4wd problem went to the dealer this fall. It didn't bankrupt me, and the mechanics found several other things that needed attention as well. My wife found me much more easy to be around than if I tried the repair myself.
If what you describe happened to me, I'd be tempted to remove the plate where my range selector lever is attached to see what I could see, but I already know not much work can be done through the top of the transmission. I also would not disassemble anything unless I was following a disassemble procedure in my repair manual. Be aware that most cover plates have gaskets under them. You can't remove a cover without replacing the gasket.