Here's the view from my bed this morning, looking up.
The ceiling fixture used to be a dim little light fixture whose power cord was threaded through a little pencil hole in the plaster, and that was screwed directly into the plaster. Last summer, I kept my room cool (?) with a window fan, which was noisy, and promised myself I'd install that ceiling fan soon. But that was before I realized there was no fixture box up there.
At any rate, I hired my favorite team of household do-everything guys, Nate and Todd. They sliced holes in the plaster, installed a solid fixture box that wouldn't come crashing down on my head, ran a few modern wires through the ceiling, installed a new switched outlet and switch in another part of the room so we could add reading lamps, and repaired the plaster. Oh, and then they hung the fan because even though I could do that part, they were already there.
It was a bit pricey (almost, but not quite, $1000). But I love my ceiling fan; it's beautiful and quiet and makes sleeping in hot weather so much nicer.