The headlight assemblies literally sit in behind the top of the bumper. I dont believe its possible to completely remove thelights without removing the bumper. Good thing to ask as installing the bumper is time consuming.
When you do get to the front bumper I believe the easy way is going to be to mount the two corner suports and the center bumper to frame rail supports to the bumper, then with help place the whole assembly up and you only have four bolts to deal with. This is how I ended up removing mine after a lot of bloody knuckles trying to remove just the bumper by itself.
harvey---install front bumper with center brkts only---adjust bumper and tighten well---remove assy and install corner braces---if any holes do not allign , elongate holes/shim as req'd---reinstall as complete assy----final adjustment with "hustler bar"