I bet you've figured this out already and the creeek in my neck is for no
good reason. However, it appears that it is mounted with a cluster of relays above the interior fuse box (1 o'clock position). I suspect it's the
one of three relays nearest the driverside fender and fuse box. Most likely the smallest one closest to you.
To make positive ID of the relay, rest your finger next to the realy while activating the horn. Assuming the relay coil is good, and it's just a bad contacts, you should feel the relay activation.
I'd remove the nut or nuts holding the relay bracket in place to remove the horn relay if that's your intent.
Horn does not work?
If so use a jumper(12 gauge wire/
I put the jumper to the horn note and the other end to ground..... If it sounds, then you have bad ground.
The relay in under the steering column....