>They said the motherboard's fried, but because they saw this one chunck of plastic missing on the bottom of the laptop
gawd, what a bunch of sc**bags!
if they say the mobo is fried and not related to the damaged case, just fix it already. have you tried speaking w/compaq directly. if it's still under warranty, maybe you'll have better luck with them than the ones at school.
laptop parts (aside from standardized stuff like ram, hd) usually have to be ordered from authorized parts distributor of the manufacturer which typically means that it is not available to the general public and are quite expensive to boot.