Golf's Cambelt Drive

I RECEIVED a letter from my VW dealer stating that the cambelt on four-year-old Golf diesel, which has done only 55,000km, should be replaced every four years or 105,000km, whichever comes first, and that failure of the cambelt could cause major engine damage. I am told it will cost $900, but if done next month will cost only $700, including water pump replacement and safety check of the vehicle. Is this really necessary with the low kilometres it has done?