removing the bumper is not necessary, but if you have the determination, it does make it easier!
otherwise, simply loosen the bumper relocation bolts (two on each side) and let the bumper slide down until it stops (will give you about an inch and a half to 2 inches). now you can get to the bolts from underneath with a wrench (i highly suggest a ratcheting wrench!). the drivers side bolt is pretty easy, but the passenger side has the small A/C core directly behind it where you would like to have your hand while wrenching, so its a bit more tedious. After you get the bolts out, you can get the tabs in place by sliding them from each fender well through the larger gap you made between the bumper and grille, all the way to their positions. stick the bolts back through, tighten 'em up, lift the bumper again, and tighten the bolts, and youre set!