I wouldn't go spliting the tractor just yet. A lot of tractors have a problem with the clutch plates sticking together, especially when the tractor isn't used often. I had a Ford that would have a struck clutch after sitting only a few days. Often you can break it loose by starting the tractor, slipping it into gear at idle, then driving around while applying the brakes. Often the shock of slipping it into gear will break the clutch free.
If there is any kind of inspection plate or access hole you can also try tapping on the clutch with a hammer and pin. This worked on my D12 which had a stuck clutch when I first got it.
If you have frequent re-occurance of this problem, you may want to use some sort of blocking on the clutch pedal so that the clutch is disengage when parked.