BuLuv

Today I brought my 06 3.5l Bu into the dealership to have the brakes checked. They ended up doing an inspection and finding a lower intake gasket leak. I don't have the best knowledge on cars, so I came here for help. The car runs perfect. I didn't suspect anything was wrong except needing new brakes. I even made the guy show me the leak and everything. It was a Chevy dealership and they estimated that the fix would be $680. Is this a fair price? How urgent is this repair? Again car drives great and there are no check engine lights on. Thanks for any input!