Not too hard, but not stupid-easy either. I have big hands that got scratched up pretty good, since the back of the grills are unfinished and sharp.
Make sure you get the tabs IN the slots. The slots are small enough that you could (and I did) wedge one of the tabs outside the slot, bending the slot a bit. Nothing broke, but it did require re-seating (more cut-up fingers, argh)
Be careful about the two middle clips (at the very least) that the torx screws go into. They're just loosely slid into place, and I bumped one and knocked it off, to drop into the bumper. Took some fishing with a magnet to get it out (more cut fingers wtf!).
Overall though, easiest mod I've done, save for the blood.