Deer hits my car, i need help!!

unless you go off roading you don't really need the engine guard, its possible they help with aerodynamics and removing them may lower your highway mpg by 1 but it shouldn't have any effect on your city mpg. I drive so rarely on the expressway (that's why I own a prius for the city mpg) I just remove them to make my maintenance easier, that undercarriage engine cover also traps in moisture meaning the components dry out much slower, thus speeding up the rusting process, get rid of it. (I think its held on my plastic clips)

bondo is for dents and chips, you have a crack in your bumper cover, you have to buy a fiberglass resin repair kit, you want to make the repair on the other side of the bumper and removing the bumper cover is a PIA, if you have ramps and a trouble lamp you may need not remove the bumper cover, depending on how small your hands are and how good your dexterity is at working in tight spaces. (its kind of like making paper mache with layers of resin and cloth)

A repair like this is definitely worth doing yourself because its so low you don't have to get it 100% perfect, and its almost inevitable no matter how safe you drive that something else will eventually happen to the bumper, and if the next accident is bigger you will get a new bumper professionally installed and painted and clearcoated . . . hope this helps.