Welcome to the sport. For starters, post your question to boatertalk
; MtnBuzz is generally a mountain-west site, boatertalk is largely populated with east coasters who will be able to give you some more localized advice.
The dagger GT would be a good beginner's kayak.
My advice would be to take some lessons, or, failing that, find a local club (again, try BT for the club bits, they may be able to point you in the right direction). They'll help you with the basics.
Generally, no, you don't need to make any reservations, and it doesn't cost any money beyond equipment and transport. As for what class you're starting out with, if you mean the river difficulty sort of class (and not the instruction type), it all depends on your ability and preference, but class II moving water will give you a good place to start some eddy turns and the more basic moves before moving up.
Also, be very, very wary about the dam in your friend's back yard. Lots of small dams create hydraulics that kill people, even though they look like they only drop a foot or two and couldn't possibly be a big deal. You may want to find another place to practice if there's a chance you could end up in the dam. They're referred to as drowning machines