Problem with horn switch and clock spring

At first, my horn would not work when the steering was in the normal drive position, it worked only if was rotated 90 degrees. Now the horn is not working at all. All other controls, radio, cruise control etc, are working fine. The air bag warning lite is not on. I have someone who said they would replace it for me but told me the part is $500+. After looking at the prices on various sites I thought this was a bit out of line. I don't want to try this on my own, for reason if I mess up i could 1 deploy the air bag by mistake or 2 not have the air bag work when i need it to. Plus I most likely don't have the proper tools. I want to make sure that I get the right part for him to replace it the first time and not have to wait for the correct part and be without my work truck for an extended period of time. Any help would be much appreciated.

Joe