Most likely it will need to be split. It is possible the problem would be under the shift cover or under the rockshaft housing. Does the shift lever go into the position for 1st gear and tractor won't move, or will he lever refuse to go into the 1st position? Is the serial number above or below 350,000? If above 350,000 it may have a synchronized transmission. Either way, I would remove the shift cover and rockshaft housing and see if you can identify the problem from there. It could be there is something broken that is blocking the shifter from moving. Those transmissions were pretty bulletproof. I don't recall ever having one that would not engage 1st gear.