Any tips on how to clip the lower part grill back onto the bumper ?
 

I pushed the bottom half of the grill in now I can't pull it out & clip in back on because the grill is hanging higher than the clip. Is my only option is to remove the plastic under the car so I can get my hands inside the grill?

Nope. Just push up on the bottom of the bumper and snap the grill in.

this might sound crazy but this is how i did it:

take floss (the stuff you use for cleaning between teeth) and then thread it around the white knobs that snap into the grille.
pull it up with one hand and then pull the grille in with other.

so. use floss.