Well I plugged the window switch back in, and sure enough, the window now functions up and down correctly. I guess that guide piece fell (rusted) out of place, and was obstructing the window from going down all the way.

So, now the question is where do I get a new one that isn't all rusted and screwed up? I guess I'll have to check out the local salvage yards. I'm not even sure how the guide piece is supposed to be secured into place, but I guess I'll figure that out...