The 105,000 limit stated by VW is an optimistic estimate and there have been documented cases of failure well before that. Most people recommend belt changes around 60-80k miles. IMO, you should change the timing belt (and associated belts/hoses, etc) both as a function of distance and age.
You should plan on changing the water pump, tensioner, and all hoses and belts that usually require a lot of labor to replace as you will just end up paying for the parts if you replace them at the same time as the timing belt.
You can get timing belt kits from ECS tuning and other german car online stores - search the B5 archives for more information on this.