Once again, the car seems to be overall in decent shape. There just seems to be 101 small jobs to do to bring it up to its former glory... and I look forward to jobs well done (to quote Edd China. BTW, I like Ant Anstead too)
The first will of course be getting my gas tank professionally fixed. I'll be dropping that off tomorrow.
Beyond that, I figured out what the problem was with the horn: there was a broken contact spring but also a missing insulating spacer. However, before I order that part I need to make sure there no other bits I might need like perhaps replacing the ignition key or connector, etc. It is like a puzzle where you first have to figure out what pieces you need...