The horn fix scheduled for today was, overall, a bust. I got the wires hooked up, the horns in place and tested it out. The relay sticks closed - meaning that I can't stop the horns unless I disconnect the battery. It wound up being handy that I have monkey arms and the back seat was flipped up. I suspect that it's the ground path because when I grounded it to something else, it worked fine.
With the help of someone who's been down this path previously, I have a few more things to test out tomorrow when I can get back into this again.