1. Buy a Haynes Manual.
2. Hire the timing locking kits from a hire shop (ESSENTIAL!)
3. follow the Haynes instructions
4. Replace the water pump and belt tensioner at the same time (as the water pump fails around 100k and the tensioner can cause belt failure too).
Job done!
You do not need to remove the engine, just one mount and remove the rubber mount block then twist the engine aside to gain access, not easy but cheaper than a trip to the dealers! (and way cheaper than letting it snap!)
SteveP, July 2009