I think you should be able to take the corner bumper filler (urethane corner piece) off or at least take the 3 fasteners off at the lower vertical edge where it meets the fender, and then remove the fasteners behind the corner filler behind the little horizontal grille. You then maneuver the corner filler out of the space it's in by weaving it from behind the front of the bumper and then off the fender. This should then allow you to remove the 3 bolts holding the horizontal thin grille on. Then remove the chrome trim "dog leg" Z-shaped trim since that overlaps the chrome trim you were needing to put on underneath the headlight bucket. once your missing piece is on, then it's the Z- shaped dog leg chrome, then the black thin grille, then weave the corner filler back into place.
I can't remember if I did all this before the final alignment of the front bumper/center bumper filler assembly. If it seems too tight to weave the corner urethane piece out, you may need to loosen the bumper and pull it out some.