I attached it with double sided tape I got from Pep Boys. It was specifically for emblems and decals. I had my doubts as to how well it would hold up, but it's been on there months now and hasn't budged.
As for the headlights, they were painted on the inside to color match the rest of the truck along with projectors retrofitted.
Mods: 18" Magnaflow; Retrofitted and color matched projector heads. Debadged. Lamin-x on lights