Another new guy here. I went with the CX as well and yes I had to reattach the fly bar after my first few crashes. It should just snap back in position. Just make sure the little link piece from the Flybar to teh rotor (not sure what teh proper name for that piece is0 is properly attached or the Heli will shake in flight. I noticed it sometimes comes lose from the fixing point on the flybar itself and just needs to ne pushed back on till it clicks solidly in position.

Spares wise I bought an extra battery but may pick up some spare motors, Fly bar and possibly drive gears but will probably wait till I really need them

Hopefully some of the experts here will give some other suggestiosn based on their experience.