Possibility number one is that you had a low beam out already but didn't notice - it's pretty common. So when the second one burned out, it went dark. Check the headlights themselves first.
Second possibility is the harness connector for the front wiring harness, which lives just behind the front bulkhead, on the driver's side beneath the air cleaner. Corrosion is very common on that connector, and it can cause all sorts of light problems. Even if it's all right, now is the time to clean and grease it.
Finally, of course, there's the dimmer switch and all that stuff, but first, get a test light on the connector mentioned above, and see if there's voltage at the low beam terminal. If I read my FSM correctly, that's the one with the violet/white wire going to it. You can double check that by turning on the parking lights first. There should be voltage at one terminal, and none at the others. That's the parking lights, and I think that will be a dark brown/red wire. Then turn on the headlights at low beam. The correct terminal is the one that now lights up. If you're getting voltage there, then you need not trouble yourself with switches and relays and stuff like that.
Keep posting if difficulties persist. I have a '95 FSM and can continue to trace wiring diagrams if necessary.
