I don't think you will have to remove the steering wheel, which would require a steering-wheel puller. Just take off the cover and fix or replace the defective horn-button mechanism.
If you do pull off the steering wheel, make sure that it's centered when you reinstall it. Centered steering wheel doesn't mean the steering wheel is perfectly straight -- it means that there needs to be exactly equal number of turns to the left and to the right from the steering-wheel position where the wheels are straight. It's probably already centered; so, just mark the current notch, and if isn't, you would have to not only recenter the steering wheel but also have your front toe readjusted, as the two are obviously related so that the steering wheel is both centered and straight. Again, I doubt you will have to pull it off though.