One key symptom for the failed steering shaft bearing in my case is that I could move the entire steering wheel left/right/up/down fairly easily, and even out a short distance if I pulled enough. There was clearly a major problem! The grinding noise I experienced was probably the piece of plastic jutting out from the back of the steering wheel (part of the turn signal cancel mechanism) rubbing directly on the bearing area -- the entire steering wheel got pulled down/in when the bearing failed.

I'd say that, IF the noise is coming from directly behind your steering wheel (and not something related to the rack, suspension etc.) that possible culprits include a bearing going south, the horn contact, or the signal cancel mechanism... really hard to say. It could even be the base of the steering wheel hitting the pod. Give it a really close look & listen. It's also quite easy to pull off the wheel to have a look, at least with no airbags!

1) Remove wheel (rotate to level first) and circlip behind the wheel. In my case, the inner race of the bearing had dropped down the steering shaft, so the circlip was not supporting anything and was easy to remove.

2) Remove turn signal housing. In retrospect this may not have been strictly necessary. The housing is held on to the end of the steering column by a clamp. However, in order to get the housing out of the way after you loosen the clamp, you have to loosen up the pod and pull the pod forward ever so slightly. There are 4 bolts (2 normal hex, 2 long Allen head) accessible from underneath the pod... remove them, then pull straight back on the pod about 1/2 or 1 inch. That allows enough room to remove the turn signal housing. (I had already removed the 2 hex bolts to remove the two plastic plates that give access under the pod anyway).

3) Remove old bearing outer race. This is the real crux of the fix. I couldn't pry it out with a screwdriver and I didn't have a bearing puller... even if I did, the outer race of the bearing had disintegrated (the small lip on the outer race, the one down the steering column, was virtually gone. This allowed the inner race to slip down the steering shaft and cause my problem). There is not a great deal of room and I did not want to use a cutter or blade of any kind for fear of creating contamination.
As it turns out, it is fairly easy because the metal outer race is both thin, somewhat malleable, and when tweaked too far will simply break. I first used an old jeweler's screwdriver to force my way between the race and the steering column, then inserted progressively larger screwdrivers (which kept breaking off chunks of the race) until I had broken all the way across. The remainder then just popped out.
As I mentioned, it might be possible to do this without removing the turn signal housing.
I also fished out all remnants of the inner part of the bearing from inside the column.

4) I inserted the new bearing and tapped into place with a piece of wood. I found something that was more or less tubular and would fit over the steering shaft, and had a flat face. It drove in easily.

5) The final trick was getting that circlip back into place! As Jim indicated above, there is a spring which pulls the steering shaft in. Warning: It's a pretty strong spring! A prior post suggested that putting the steering nut on the shaft, grabbing it with a huge channel lock, and pulling with all your might would work... though I think there was a mention of a second person to help as well! I couldn't make it work. Instead, I inserted a small socket as a spacer between the nut and the bearing, and cranked down the nut until the circlip groove was exposed.

6) Re-install turn signal housing, pod, wheel in same location etc.

Thanks to all the prior posters who made this fix much easier than it would have been otherwise!

I knocked the pressed in bearing out with a screwdriver. There is a slot at the top of the steering shaft, maybe designed for access with some kind of tool. I knocked it out toward me very carefully than grabbed with needlenose plyers and worked out all the way around. Tapped new one in gentley. The hard part as you say is putting the sleve on and then somehow getting the c clip on. I did it the hard way. I put the sleeve on, threaded the 27mm nut on grabbed it and pulled out as my wife pushed the c clip on. Only took about a minute but man, it was pretty hard to grab on the nut and pull at the same time.
Interesting is the idea that a non-cancelling turn signal might involve that upper bearing and also that others have replaced the bearing only to have it fail again. The manual in 48-25 and 48-30 gives some kind of important axial play adjustment procedures and this dire warning: "If there is no axial play, it must be adjusted otherwise the new bearing could be destroyed in a short time".