Coincidentally my daughters car is having a similar problem. Diagnosis was big bucks to pull the tank and replace the fuel pump. Second opinion on the way from a gm mechanic friend that does work on the side, out of his house! Has a lift, the tools, knowhow and discounted price. Hope this is not as wrong as the mechanic at the dealer post.
This link below might be of some help as a reference. How the Chrysler fuel tank evap system works. Uses pressure rather than what most other cars use, vacuum.