2005 Chevy Vivant Fuel System Noise

After stopping the vehicle a series of short clicks are heard from under the car. There may be as many as 50 of these and they last from less than 1 minute. Six months ago it started on an infrequent basis and now it is every time the vehicle is stopped. Garage says it is in the fuel system and has to do with a valve or the vacuum system. Garage relates Daewoo, the manufacturer of the vehicle, issued a fix for the problem but that was already done. Garage wants over $900 to fix the problem but says not to do it as there is no impact on use of the vehicle and vehicle is safe to drive.

Is the garage correct? Is there an inexpensive fix? Will the car just stop running at some time?

Thanks,
Leo at the shipyard

updated 9/9/09
Took the Vivant to another Chevrolet dealer and they immediately knew what the problem was as it is common for this car.

On the top of the gas tank there is a vacuum control valve that was stuck.
All that was required was to remove the gas tank and clean/ renew the valve.

Do not know if it is a manual or electric operated unit. Cost was about
$125. The $900 original estimate was to replace the entire gas tank assembly

and fuel lines to the motor. A real rip off by a Chevrolet garage.