BigTime Muscle RC Electric Car?

I have a 1:18 electric RC car. It is a Big Time Muscle tm and is from Jada Toys. It has a 6.3 v battery and runs on a fairly fast motor. I need to know if it is possible to install a bigger motor. If i put a bigger motor do i need a bigger battery ? since im getting more current and voltage should i change any other components to avoid a burnout of some sort such as resistors, capacitors, etc. ?
In other words i am trying to make this sucker faster and have more power when going through unsmooth terrain

Sure you can.
If you put in a larger capacity battery with a higher voltage that will increase the power. A 7.2v stick pack like one of these would be ideal…

http://www.modelsport.co.uk/?CallFunction=Category&CategoryID=99205510

Just be sure to keep all the connectors from your existing battery, they might be different if you buy a new battery.

If you plan on changing the motor, you might have to buy a new electronic speed control to suit a more powerful motor. Also, motors aren't all the same size. 1/10 scale cars have 540 or 550 size motors, 1/18 scale cars have smaller motors probably 370. The number refers to the size of the motor casing or can, so don't think it's going to be less powerful because of the lower number.

If you change the motor and not the speed control, you'll risk frying the motor or speed control. Or both.

This motor would be perfect, as it's designed for 1/18 scale cars anyway…

http://www.modelsport.co.uk/?CallFunction=ShowSpecification&ItemID=26672