Just thought I'd post a quick update. I was easily able to swap out the light fixture for an electric outlet, and it all seems to work fine now. I don't think I clipped off quite enough of the wires, so it was a bit of a tight squeeze to get the plate on at the end, but I managed.

Next step: building the grow cabinet. I'll update once I make some progress on that front. Unfortunately I don't think I can post photos yet, but I will try to do that at some point.