Steering Fluid Change 2000 E320

This might be an easy question, but how do I change/replace the steering fluid on a 2000 E320? I know where the steering fluid housing is with the dip stick level check as the cover.

I am hearing minor squeaking noises when I turn the wheel in either direction at low speeds or stationary. The steering fluid change may not eliminate the noise, but I figured it wouldn't hurt. I have checked the fluid level and it is at max level.