On instruction #6, what that doesn't say is once you turn the steering shaft all the way till it stops moving (either left or right), place a mark on the shaft and housing. Then turn it all the way in the other direction while counting how many turns it takes to get to the other stop point. Once you know how many turns it took to get from one end to the other, divide that number in half. Then turn the steering shaft back the original direction that many turns and stop. Remark the steering shaft and housing to indicate that is the steering gear center position. If it was me, I would jot a note down to help me remember how many turns lock to lock and how many back to center so if the gear gets moved, you can easily run it through to get it back to center before connecting up to the steering shaft.
On your question about #9, unless installing the rag joint to the steering input shaft interfers with getting it mounted to the frame, it should be just fine to install first IMO.
Hope this helps answer your questions.
