After seafarers long winded but basically correct answer I will answer your question.
Should be renewed at 70,000 miles or every 5 years whichever comes first.
It is a cambelt on your car, it needs renewing with a full cambelt kit, this includes the cambelt, tensioners and a new auxiliary belt, it is also advisable to get a new waterpump fitted at the same time.
Renaults would charge around �475 for that but a good independant garage would charge about half that amount.