HELP!! uneven brake ware

i got a brake job done about 3 months ago. and the front left is so gone that it started to cut into the rotor .. half of my new front left rotor is gone now. but the rest of the brakes perfect .. almost like new.. would a bad brake job do this? or is that particular caliper gone?

i own a 2000 GT Vert and i do drive allot about 100 miles a day. but that is no reason for one brake to waste like that.. any help would be appreciated..

caliper rebuild huh? sounds like that would be my problem.. is it dificult to do a rebuild? were can i pick a kit like that up? pep boys? or should i take it in?
since i have no choice but to do an entire front brake job.. i plan to get new Ford Racing cross drilled and slotted rotors some Hawk hps+ pads and steeda brake lines.. i also plan to re-bleed the entire system and switch form dealer brake fluid to Motul fluid... is this a good upgrade?