You don't need to do step 6 in the detailed instructions (drain washer fluid). The hoses that go to the headlight washers (if you have them) have press-n-release plugs on them. The only drip will be from what's left in the sprayers themselves.
The grill replacement is (in my experience) a 2 person, 3 hour job from start to finish that must be done very carefully (do not rush) or you will mess up the bumper cover and you will be crying.
One thing to remember is that the cover itself slides into and interlocks with the front of the fenders. Be sure the bumper cover tabs (and mating area on the fenders) are clean when you slide the bumper cover back into the front of the fenders.
If you have a factory front plate mount that a dealer screwed in, you can move it below the new grille (after the grille is installed) by trimming it with a razor blade to fit the taper of the bumper cover. The factory screw can be used too, and it will cover the holes that the dealer made.
If you install a TRex grille, be prepared to take a lot of time to ensure it's lined up properly, otherwise it will look like it was installed more to one side than the other.