Have the dealer pull up the receipt on their computer.
Check to see what was replaced. (the basic rule is replace: the timing belt, tensioner, and water pump; why? all those are easily accessible when replacing the timing belt. The parts aren't too expensive. But, it's the labor that costs you $$$.)
Also, what do they mean when they say "the tensioner is leaking"? (it's a pulley that rides against the back of the timing belt. Nothing to leak from that. Maybe, they meant the water pump is leaking?)
take care,
ChrisS