Just did mine today. Yeah, the top tab is a pain because you can't see it. Basically just angle your flat head up and insert it as deep as you can to catch the top edge of the tab. Then twist. It should pop out slightly immediately. And then the bottom is a no brainer.
Once you get your cover off, the next hard step is to unscrew the far Torx screw holding the light. You can't see it so you'll need to feel for it with your finger and guide the screw driver in to seat properly.