Remove the horn button.
Unbolt the 19mm nut.
Using a sharp scribe, mark the wheel so it can be reinstalled in the same location.
Using a large center punch and a hammer, get both of your knees against the back of the steering wheel so as to push against the back of the wheel on the left and right side.
With a good smack, the wheel should pop right off.
The horn ring and contact pin will be accesable and can be greased.
The contact pin kit is avaiable from the dealer, however, the contact ring on the rear of the steering wheel can be extended to gain additional service by removing the three retainer screws and spacing the ring away from the steering wheel. This will in turn preload the contact pin and the horn will once again work.
Thanks Marlin. My steering wheel looks like the one above. Was it and the Tach only part of the SR5 package in 1980?