If you haven't flown it before, check to make sure the electronics are responding correctly - a bad crash can leave servos pretty shaken up and lead to fatal glitch in the air. Just power on and then move your controls around, first subtle inputs then bigger inputs. Also, check if the main rotor shaft is bent. If a vibration becomes a violent shake from 0% to 50% throttle then the shaft may need to be straightened out again or replaced. Lastly, check the rotor head assembly for minor cracks in links or anything like that. This is essentially a pre-flight check, I suppose.

As for alternate parts, I don't quite remember what can be borrowed from E-Flite for the Axe, but going through [link=http://www.rcuniverse.com/forum/m_5579975/tm.htm]this thread[/link] will give a good idea of what you can use.