How to replace 1993 Pontiac grand am brake fluid?

you never want to completly empty your resevoir. air bubbles will get in your brake lines and will make it super hard to stop. you should just add fluid. if you really do want to change it all out then you need to disconnect the brake line at one or all the tires and pump the brakes until its all out. but when you go to put more in then you will need to bleed the lines for any air bubbles which is a bigger project then when you started.