I'm not that familiar with your model tractor but there should be a drain plug at the bottom of each "transfer case" at the wheels.
So it sounds like you did a partial drain and fill. That is far better than no drain and fill at all. Whether you want to go through it again is up to you. It is probably fine until the next scheduled maintenance.
You didn't mention what fluid you used or how many hours on the tractor. If the fluid was the same as in before, UDT or gear oil, then they will mix. If not, then a drain and fill would be indicated. If it was the 50 hour service, personally, I'd do it again.
Also, check the oil level after a few hours of use. It takes a while for it to work in and around the enclosure. Lots of folks end up with low oil levels...even dealerships.