need fiberglassing help

Yes, both would have different rates of expansion/contraction and you may get a stress fracture at the joints and paint will chip.
Not sure how the lights look like, but you maybe able to contour the ‘plastic’ bumper around the fog lights using a heat gun.

need fiberglassing help

ive decided to get projector fogs and fiberglass them into teh bumper. the only problem is ive herd that fiberglass and urithane bumpers dont go well together( cus the bumper can flex and the fiberglass wont and crack). does this sound right?

i was thinking of taking the tow hook cover things taht are in there now, cutting any exess junk out, and fiberglass the lights right into those. then they would jsut snap into the bumper

I think you're talking about the fog light covers (black) that are in your bumper; they have foglight for your 01/02 bumper, but very expensive, upto $200 in cost.

It should work like you said using the covers as a template to make custom holders.