It's all reassembled and working - thanks for the assist!
I found that disconnecting the shelf for the fuel tank & setting it aside on the front tire (no need to disconnect or drain),
disconnecting the shelf/spline above that (though which the steering shaft passes) & bending that some,
I was able to slide the shaft/spline out and the new one in at an angle.
While the shaft/spline was disconnected I made sure that the front wheel assembly turned freely, spraying "dry"
lubricant (molybendum/teflon) into the joints.
BTW: I used vice grips on the shaft/spline screw at the bottom.
Steering is nice and smooth & I was able to get a bunch of mowing done until a t-storm arrived.