you can adjust the linkage along with the trim on the transmitter

RTR servos are usually crap so its a good idea to replace them
a good servo is the futaba 3303 it is about $30 and it has 99oz of torque with a 4.8 volt reciever pack and 124oz of torque with a 6.0 volt reciever pack this servo would be good for steering and brake/throttle

also-i highly recomend a 6.0 volt reciever pack if you dont already have one