Thanks, guys, you rule. I'm still not entirely sure what I've got--I know that I do NOT have a cup at the bottom of the headset. When I got the top unscrewed and was able to push the stem down, the bearings came with it. There's nothing underneath for them to roll in, just the frame and steerer tube.
Here's a pic of the front, sorry this doesn't really have much detail. Those things at the top and bottom of the front tube aren't cups; they screw on to the frame, but the bearings are are completely contained within.
You can see things better if you zoom in (just keep the mouse over the pic in Firefox and left-click).
Unscrewed, it looks like that earlier picture.
But, you're right, I do need to take it in. Plan on doing it this afternoon.