It has been probably 40 years since I have had the transmission on one of those apart. We are trying to finish planting corn today. They are talking rain this evening and I will need to read the procedure again. However you will need some spaner wrenches and you will need to split the tractor to solve your problem. More details tomorrow if it rains tonight.
Also if you prepare to split the tractor if you can rig up a set of supports that are adjustable in height it will help.