Ponchogl - While your applying some of your chosen lubricant to the steering wheel nut, may be give a little shot to the screw that holds the horn wire retaining plate on the top side of your steering column under the dash. My previous experience has found that screw to be usually tough to remove due to some rust corrosion that forms over the years. A dab of "juice" will help it come out when the time to remove that plate for the mast bearing/horn wire replacement.
The plate and screw look like what is pictured below.
