1) Unless they've changed the design drastically since I last had one, I think you'll find that the lockring has nothing to do with the driver 'staying in' The lockring is what clamps the sprocket to the driver and stops it from coming undone. The driver can be removed by simply taking the wheel out of the frame, undo the bolts and remove washers/spacers, then simply pull it out. Rotating the driver at the same time may help 'unbind' the ratchets from the teeth. Dont need to worry about anything falling out, it shouldn't and if it does its because something is broken, not because of something you did whilst trying to take it apart (hopefully)
2) How do you service a shell - A hollow piece of metal? If you mean the ratchet ring, again how? Theres not much you can do to it except brush its teeth with a toothbrush and check for wear
Do a search on this, I put up a lengthy fool proof guide to how to do it
Here