I removed a fluorescent light fixture from kitchen but I'm not sure the work box will support a real light fixture. The work box is round and plastic. The fluorescent light wasn't even held up by the work box, it was attached directly to the ceiling.
I've installed light fixtures before to metal work boxes and its usually replacing another light fixture attached to the work box, so I know they can handle it. For this one I'm just not sure.
Here are pictures of the work box in question: