You're in for trouble. Those spoilers are covered in 3m adhesive on the bottom of them. They're a nightmare to remove, especially if you're trying to not have to re-paint it.
Fishing line helps, but be careful not to build too much heat.
Might be worth paying a shop on this one. You're going to have 4 holes to deal with too. A couple gloss black vinyl dots would cover them for the most part.
Edit: wait... Are you removing the spoiler, or the black plastic piece?? Lol
are you trying to remove the spoiler or the deck lid panel? if you're trying remove that panel, that's easy, it's held on with very strong double sided tape, get some strong fishing line and use it as a saw so to speak, then remove the tape residue with a heat gun (carefully) and some wd40, the bad news is, once the panel is removed, the hump will be bare, as the panel on there now has the center faux gas lid built into the panel permanently