Done.
Just installed it a few minutes ago. I love it. The black skid plate was a must to go along with the mostly blacked out grille and GMC logo.
Part number for the grill with paint to match surround (from the SLT Elevation package) is 84065168 for anyone else who wants to do this.
Job was fairly straightforward for anyone with reasonable auto tech skills. The entire bumper did have to come off in order to install the skid plate but it was a matter of six easy to get to bolts, removing a plate from each side of the back of the bumper, and a bit of wire harness jostling and nothing more. It was worth the effort.
Only thing that could go wrong is the "upper cap" (the big piece of trim between the grill and the bumper) could break tabs when removing it (worst case scenario because it's $400 and needs to be painted) OR (what happened to me) you could break one of the plastic retention pieces at each end of the upper cap. I was going to install the cap with the broken retainer but being OCD I just couldn't do it. Picked up the part at the local dealer for $17.
My stock Denali grille and chrome skid plate are now for sale. They had 250 miles on them when I took them off. Pristine condition. No broken tabs, no broken anything.
Next up, installation of the OEM Borla performance exhaust with rectangular rear-exit tips.