havoc is right about centek being dead. however, the main man of the company left and founded CZUBATECH on himself. This company is still active.
He still repairs falcons and is working on completion of te ct060 accelator.
I don't know if Rodolphe Czuba could fix your quadra. Even if this guy is something of a living legend, I don't know if he has sufficient knowledge of mac systems... ?