New Holland 688 roll/gear/bearing question

I just purchased a NH 688 knowing that it had some issues.  It wasn't starting the bale/forming a core and would plug up.  My mechanic has looked it over and discovered the "middle roll" is cracked in several places and the bearing appear to be shot.  The "stripper roll" has several large dents in it and the bearing in it are also questionable.  It's in need of a little more work that I was hoping for but I got it at a good price and once these things are fixed up it should be in good shape and last me a long time for the amount of baling I do.

 

So now for the questions...

 

Looking at the parts diagrams at Messick's it appears that the bearing and the gear on one side come as a unit.  If the gear is okay but the bearing is shot can you get just the bearing and press the old one out and the new one into the gear?

 

According to the diagram the middle roll is $1232 and the stripper roll is $777.  I've been told that the rolls are the same except the middle roll is not supposed to have any round stock on it where the stripper roll does. On my baler they both have round stock on them.  All the bearings, washers, gears, bolts etc. appear to be identical between the 2 rolls so why would one be $400 and change more than the other?

Thanks

Dave

New Holland 688 roll/gear/bearing question