Your ESC should be able to handle the motor, a quick google search threw up a limit of 15 turns.

Gear ratio is very important. What gears do you have on the car now? The car's manual or one of the experts in the Schumacher thread should be able to tell you the internal ratio of your car, it is then a case of doing some maths...

FDR aka Overall ratio = Internal ratio*(spur/pinion)