The first step to increasing the performance of any vehicle is the use of a low restriction intake system (not the manifold, yet). The most gains for a bolt on, in general, will be found with this one modification.
Franchise repair shops in general are not bad places to go. They are a by-the-book business that follows these guidelines to the "T." However, they are not without fault. First problem I have with franchises is they hire the most inexperienced people to work on your car.
Ah yes, the dealership — or its other common name the "stealership." I'm here to defend and debunk the dealership, and along the way shed light on the whole operation.