try absentmindedly backing out of the garage with the hatch still open.. "hey, I wonder why visability is so good!".... ooops replacing hatch spoiler.. fairly easy...
The piece that pops off is the painted (to match car exterior) plastic piece on the back of the mirror. The black plastic is part of the entire mirror assembly. So it's the difference between a $30 part (the cover) and a $130 part (the mirror assembly).