is it possible

[ralliart]

is it possible to change the motor in your servo to make it faster or give it more power

[SteveK]

It's not practical, if possible: The motors are integral to the servos, so you would need one exactly the same size as the old one, and likely bond it in somehow.

It's easier to just buy a whole new servo.

[rcguy2477]

You might be able to get some more speed and torque if you tinker with the motor. But if you are really that desparate for more torque and speed, just get a new servo.