RE: EsC
The stock set-up uses a 3cell lipo = 11.1 volts
The stock set-up uses an 18 amp ESC.
Therefore, you need an 18 amp or greater ESC capable of handling 11.1 volts (3c lipo)
You can get one from Hobbyking in the US for $12. It also has a battery eliminator circuit, allowing you to use one battery to power the motor and the receiver/servos.
Kurt