If it's a 2 ltr oetrol like mine the book will say 10 years or 100,000 miles, whichever comes first, but I think the generally accepted limit is now 60-70,000 miles or five years. I had mine done at 58,000 and although the belt was in good condition it was loose on the pulleys and would have come off at any time with catastrophic results. Cost ? Depends where you go. I paid a Local garage �180 last year. Make sure you get the full kit fitted, belt, pulleys, tensioner etc.