You will probably have to drill the setscrew out and remove the horn. When you get the new control horn, put it in place, with the set screw out, mark the wire of the nose gear. grind (or file) a small flat on the wire. when you install the set screw, it will go into the flat that you ground, and enable you to tighten the screw so that the wire will not turn. You should also do this on the landing gear where the wheel collars go. This is considered pretty basic stuff for those who have been doing this for a while. Plans, and instructions used to suggest this. I suppose that when ARF's started coming along, these ideas were lost in the shuffle.

If the setscrew is a bolt type, you can probably grip it with a pair of pliers and remove it.

Bill, AMA 4720