2009 CTS 3.9 Direct Injection

With the hood open, there is black trim panels that go across the top of the grille and up the inside of the fenders. These pcs look to be held in place by round plastic retainers. How do these retainers come out so the trim panels can be removed?
Once the retainers are removed, can they be reused or do they have to be replaced?

I want to paint my grille black and need to either remove the grille or at least be able to remove the Cadillac emblem.