Either the 2WD or 4WD 4 Runner is relativity simply to replace the front brake rotors. The truck needs to be jacked up and supported safely. The wheel removed, the brake caliper, brake pads and brake caliper mounting bracket need to be removed, and the brake caliper is a "slip on fit" on the hub. Reassemble and prior to starting the car depress the brake pedal several times. Then start the 4 Runner and depress the brake pedal several times. Do one side at a time as things are a mirror image one side vs the other. I agree with Fernando replace brake rotors as a pair and also replace the brake pads at this time.