To answer your specific questions:
If a single engine turbine is over torqued, where is the damage in the drive train likely to occur and which components most likely effected first ?
I would look at the tail rotor blades and associated drivetrain first. The maintenance manual will/should tell you where to look based on the severity of the event. The main rotor stuff (blades, gearbox, etc.) is MUCH tougher.
Also, which maneuvers are most likely to lead to OT.
And by "OT" I assume you mean "overtorque." Obviously, takeoffs and landings. Probably a landing gone wrong - oops! (No need for that much power in translated flight.) Left pedal turn in a very heavy hover, perhaps? Couple of different scenarios I can think of, each as "likely" as the next.