OK, after taking a little time to take the headlight out, I can confirm this is by far the easiest route. Pop out the little little plastic snap-locks (for want of the correct word) that hold the little plastic cosmetic fairing around the hood release off. Then one by one, press the little latches that hold the grille in place (there are five of them), and remove the grille. Remove three bolts that hold the passenger headlight in place (two on the inside edge, one on the top, and slide the headlight out forwards. You'll now see the horn underneath where the headlight formerly was. One bolt holds it to the car, and one cable connects it to the electrics. Note if you're replacing the horn (mine was dead) that if your replacement horn has connectors for power and ground, rather than just the single power connector, you'll need to fabricate a short cable with a couple of spade connectors to run to ground. (I didn't realise the Kia's horn was a single-connector design).
All of these instructions are for a 97 Sephia RS, and I would assume other 97s will be similar. On the plus side, if your horn is dead, you can replace it with one that doesn't sound as horribly cheesy as the original Kia horn did!