Schematic intersection.
The plastic has a number of ~ 1/2" tabs. The stainless trim grabs on to these. One way.
The position of the tabs are visible from the back of the grille. Rectangular holes.
Mine had dents that took long hours to fix.
Some kind of tool is needed. Maybe a small screwdriver and bend the tip 90 deg.
You need to get the tool between the tab and the trim and very carefully lift the trim while you pull it from the plastic.
Work your way over the length of the grille, a little bit at the time.
The tool should be on the "hole side" of the tab.
Patience here will save you a lot of work fixing the dents later...