I have just booked in my 2001 GS300 Navi in for a 60,000 mile 6 year service. Cost was very similar to yours. They also informed me that the cam belt was due for renewal, taking my bill to nearly £900 with Gold discount and me supplying my own oil. The service book says that it is 100,000 or 10 years for a cambelt change. I have a feeling that there have been many cambelts snapping before the 10 years or the 100,000 miles are up. Better to get it done and swallow the bill than to chance a wrecked engine. It will be cheaper in the long run.