I know someone that had a jeep done at zimmer gears. Pricey, but he was pleased with the work. Pm themcfarland, or edman87k5. Those are some local offroad guys that may have more info. You can also pm freshmeat on here. He is the owner of the louisiana offroad forum.
It must be electric like Ben was thinking. In that case im not sure. Was hoping it was just a popped off vacuum line, easy fix. Good luck, hope it does turn out to be simple
That picture looks like you are looking at the master cylinder. All the hard lines are for each wheel (4 wheel disc) the booster should be behind that, huge, round, black. Mounted on the firewall