I doubt that I can help you, but if the tractor went swimming, then I'd suspect corrosion. If I understand you right, the lever itself is stuck and won't move, meaning that the 3-point might work OK if you could move the lever? How long has it been since it was working right? Can you get to the lever all the way to where it's attached to the part that goes into the housing? Possibly a little PB Blaster, or even WD-40 might help.