I was able to remove the dealer's decal on the hatch this afternoon. Even if I told them not to stick it, they did it anyway.

Well you just need an hair dryer, and a car detailing product (I did use AutoGlym Rapid detailer).

First step, just heat up the decal with the hair dryer for just a couple of minutes, then pull it slowly from one end while keeping blowing hot air. It's a breeze to remove it. Then just clean the sticker residue with the Rapid detailer, and voilà!

This video is pretty useful :

https://www.youtube.com/watch?v=vdmC9oIvseo

License plate frame from the dealer came out too this afternoon