I thought I'd be able to lift the plastic shade and angle it out of the trim, but it doesn't lift at all. It slides side-to-side a bit, but the flanges are large enough to keep it firmly behind the trim. The trim is attached on the two rounded ends and doesn't seem to slide down or unclip in any way. The long sides of the trim will bend down a bit if I pull on them.
I just want to see if anyone has any obvious suggestions I'm missing before I try prying the trim off the ceiling. A lot of things in this house seem to have been done in the cheapest way possible that wouldn't be immediately noticed by a potential buyer, and I'm guessing this bulb that can't be changed without reinstalling the trim around the fixture might be one of them.