Grills go in before front bumper. The filler panels go in with speed nuts that attach to the latch assy and side gussetts, so you just need top access. The side rubber fillers attach from the top first and then to the bumper before you put it in place, extra set of hands quite helpful. This is just how I did it. But you may break the grills if you try to force them in after the fact. Keep everything on the loose side for adjustments, you'll need to align it all up.
