All good questions, and they all will be answered in the class. Your only requirement for the class is bike, helmet and hydration. A water bottle will be fine. In class we discuss the benefits of the backpack hydration systems (Camelbacks). We also cover tools, tires, proper bicycle setup, and just about any other questions you may have.
Clipless do take getting used to, but eventually getting in and out becomes second nature. They definitely are the way to go. Keep 'em for now and we can talk about upgrades.
Full vs hard tail will be discussed, and other class members can chime-in as to their preferences. Your riding requirements and where you plan to ride will greatly influence what bike configuration will best suit your needs.
Now all you need to do is register for class.