It should be replaced every 70,000 MILES om not sure about KM.
You can follow the link it gives a pretty good description about replaceing the belt.If you have anymore quiestions just post back and I will reply.
Yeah, i kinda figure that as well. But the mechanic asked for two days, since the oil seals were also affected. So, they had to drop the gearbox, and that was why it took two days. And quite a big bill, too.