Seems to me, the logic side of the board should not have been harmed by the 12v DC supply. The regulator can handle a max of 15v. The logic bus should have stayed at 3.3v with no problem.
Seems to me the only thing that could have been harmed was the servos. Although it's possible that they failed in such as way that the 12v may have fed back through the single lines to the PIC outputs. Hard to tell without some more trouble-shooting.
Have you tried to erase the PIC and reload the firmware? That might give an indication as to whether the PIC was damaged.