first try shifting the engine turned off. if it shifts easily then most likely the belt isn't disengaging all the way. may need to make an adjustment in the clutch rod to get it to fully disengage. If it still doesn't shift, I would try lubing the linkage going into tranny. They will rust in that area, and make it hard to move the shifter. As far as the locked up tranny, I would check the brake mechanism on the side of the tranny. They tend to stick when the brake is applied.