replacing brake pedal switch on astra (2000) X reg?

How easy or hard would it be to replace the brake pedal switch on my astra (2000) x reg. Would i need to take it to a garage or is it easy enough to do myself. I have replaced a rear windscreen motor mechanism before no probs and the few bulbs when they blow. Also, what is the part number for switch, how much does the switch cost and how much should it cost roughly if i got a local garage to do repair. thanks