You can place the ignition switch in the OFF position, apply and release the brake pedal several times until the brake pedal becomes firm to deplete the power vacuum
Brake Booster vacuum reserve, disconnect the electrical connector and remove the power brake booster vacuum sensor and vacuum hose and position aside, remove the brake master cylinder nuts, the brake master cylinder and support with heavy mechanics wire or equivalent, the brake booster pushrod retainer bolt, the brake booster pushrod retainer, disconnect the electrical connector and remove the stop lamp switch, disconnect the brake booster pushrod from the brake pedal pin, remove the power vacuum brake booster nuts, the power vacuum brake booster, the power vacuum brake booster gasket.