License plate light rebuild?

If it were me I’d clean all that paint of it first with some lacquer thinner to expose anything hiding under it. I think theirs a foam gasket under the lens. It may be disintegrated or hard as a rock if it’s still there. Either way theirs only one way to do it. Gently bend up the tabs and slowly work something between the lens and housing perimeter. I’d try a razor blade first. Good luck.