Have a question about struts?

National Tire and Battery is great notifying you of potential problems. We have a 2008 Toyota Sienna w/25500 miles, front tires worn (that we noticed seems more than they should be for a 1 1/2 old vehicle). NTB told us 1 of front struts is leaking oil (they actually showed me) the strut was not dry there was enough oil to smear enough off to cover your finger. Took the vehicle to the dealer and they actually told me that the front struts were NOT leaking and even told the person who worked on it to come out and tell me. I'm trying to find out about struts to see if this is a real problem or should this be pursued because I only have about 10,000 miles left under warranty? What would you say, are there any mechanics out there? Thank you very much in considering my question.