I can't visualise what you're stuck on either. I don't recall any inaccessible fasteners, but then its almost muscle memory now. A pic or two would help
The light comes out independent of the lock iirc, but the lock itself can be removed inward while the light comes outward. If you do remove the lock pay attention to the two washers between it and the sheet metal - these are needed to make it flush with the tail light.