9020 hydrostatic pump problem

[docp]

Can a worn (not sheared) pin in the pump for the hydrostatic transmission cause the pump to stop pumping? Rear lift doesn't work at all, engaging the hydrostatic shift lever causes the rear tires to barely turn, and with no power. How does a rank amateur mechanic like myself go about getting my tractor healed? Self healing hasn't happened, yet, and doesn't appear likely.