getting to the 4 screws on the bottom of the stock grill is a PITA. The chin spoiler definitley use screws or bolts, First time i barely hit a curb with mine it popped 5 of the push pins int the middle and the front of it sagged down.
ive been told the grill delete isnt that bad to put in but the chin spoiler def good if you have an extra pair of hands. and def go with the bolts, mines bolted in and ive smacked it a good couple of times and its still holdin up strong.
def dont use the snap ins for the chin spoiler, i was putting machboy's on and i broke over half of them just putting them on...of course it was freezing in my garage too, i got some black-headed screws and put it on that way