Not sure how the 92 dash is, but on my 85, 89, 90 models, you simply remove the speaker grill from the top of the dash and unbolt the speaker. You can't remove it from underneath. Be careful with the screwdriver prying the grill off. Two bolts/screws holding the speaker to the dash, then unplug it once you've removed it.
On edit: if you swung the glovebox out of the way, the speaker is up and to the left of the glovebox. You could possibly check to see that its still plugged in, but thats it.