I just went to Deere.com and discovered that a new pump is $500.
but, a rebuild kit is significantly less expensive. The kit only does bearings and seals and, since it isn't leaking and turns freely, probably won't do me much good.
At this point, I can only speculate on what is causing the overheating ...maybe some debris blocking the flow to the pump? slipping belt? Hopefully, dissasembly will reveal the cause.