I got it fixed. Overall not too bad of a job. Took about 4 hours start to finish. Of course, now that I did it once, I could do it again in about an hour. In order to save the rest of you from spending more time than necessary I will try to document what I did.
I did not have to take off the steering box. It ended up being pretty darn simple. Removed the bolts (4 of them) from the opposite side, pulled out from the right side. Put new one in.
I made it a little more difficult on myself, as I removed the dash, gas-tank, throttle plate, in order to give me full access. I'm not sure it was necessary or not. Definitely wasn't for the removal of he sector shaft, as the broken one wasn't that long and wouldn;t have interfered with anything. Only added a couple of hours in any event. Since I drained the tank, I cleaned it up, replaced my fuel filter, etc.
A couple of things to look out for. BEFORE removal, tie the steering wheel in place. Then mark the sector shaft position as it relates to the housing. I, of course, did not do this. Added about 30-60 minutes trying to figure out the relationship of where the gears meshed. Mostly trial and error. Can be done, but save yourself the hassle.
The original part number is not made any more. The replacement crossed reference to a Kubota part number (don't have it in front of me, but I'll post so it can be referenced). I was a bit skiddish about ordering as it wasn't returnable, but it worked out fine. The part was just a tad longer than the original, so I had to clearance the frame brace notch where the steering rod travels by your left foot. Only had to grind 1/8" - 1/4". Not a big deal.
Last thing was that in looking at the steering travel for the clearance, I discovered that the steering stops on the front wheels were not set. Don't know if they were ever set, or just backed off over time. But, regardless, this seemed to at least contribute to the sector shaft failure, if not directly caused it, because what would happen is if the steering was full to one side and the wheels took any force (ditch, bank of snow, pile of dirt, etc) the force would radiate up the steering linkages and put perpendicular force of the sector shaft. So next time you are doing maintenance give the stops a quick check. May save you some headache down the road.
I think that's it. I'll post the part number and the price (~$150) when I dig it up.