How do you change brake booster on a 99 mercury villager?

To change the brake booster on a 1999 Mercury Villager, first, disconnect the negative battery terminal and remove the master cylinder from the booster. Then, detach the brake booster by removing the mounting nuts from the firewall and disconnecting the pushrod from the brake pedal. Install the new booster by reversing the removal steps, ensuring all connections are secure, and finally bleed the brake system to remove any air.