This knob helps limit servo movement - it also will have to go. We'll get to that in a minute.
Alrighty then... let's remove any stickers and such that might prevent us from getting to the guts of the servo.
Remove any screws or bands that hold the servo case together.
Inside you'll see a tiny circuit board, a motor, and a potentiometer.
We'll remove these three wires coming from the potentiometer.
No worries... just cut through them.
But be careful not to damage the wires coming from the motor.
Depending on your servo, you might have to get at the potentiometer through the top.
Make a mental note of the gear configuration - you're going to have to put them back in their proper order.
Gently pull out the gears and potentiometer. Minimizing movement of the press-fit gears now will mean a more solid / reliable gear-motor later.
Time to get rid of the wires hanging off the potentiometer.
Clip them as close as you can to the base of the potentiometer. Try not to damage the housing, it's typically made of brittle resin or plastic.
One of these things is not like the other... the guy in the middle is the first key to making a solid gear-motor.