how do you replace brake light switch on 1996 citreon saxo?

my brake lights stopped working.when a friend checked he said water was leaking through to the pedals and has probably blown the brake light switch.he said it shouldnt be hard getting and fitting replacement switch.he also said that could explain why reverse lights went about the same time.bulbs and fuses are ok.is it the switch and can it be fixed? i dont have the money to take it to a garage.please help