I have not replaced one but have had mine completely apart for restoring. The coils are easy to replace, if you have a replacement. If you have a replacement you probably have the entire horn so just swap them out.
yeah, I knew you had this written up - I took it all apart
measured continuity and such - but when hooked up, coil just fried
the reason I was asking is that I have the high horn installed and remember having (if only I could find it ) a low horn where the ear-looking part is cracked - I thought I could mate the two and get a 'new' high horn out of it
I don't have space for a second horn, that mounting point holds the radiator overflow bottle ;p