RE: Use of crashed components.
Some Tid Bits
After a major crash every component is tested like this.
The receiver goes back to the manufacturer for testing.
The servos are put on a testing machine to verify the gear train and torque.
Batteries are cycled and mine are all wrapped in foam.
Engine is removed and put on my test stand and rechecked for performance.
If there is a typical problem it is in the servo gear train from what I have seen.