#1 you always get better service from a good local shop than the dealership. this is why 80% of their business disappears when the factory warranty runs out. this does not mean "Goober Lube", this means a real shop, that's locally owned by someone that has a great reputation.
#2 "might" does not have anything to do with reality. a second opinion is always a good thing. if your doctor told
you that you "might" have a brain tumor, what would you do?
#3 how could they cause this "maybe" leak?? you don't know for certain that you even have a leak, yet you've already
cast doubt that they somehow have deliberately damaged your car. it's called "ever since" syndrome.
#4 oil pan gaskets, valve cover gaskets, water pump gaskets
will all eventually leak. they do not wear out. have you ever had a faucet drip at your house? same thing.