basic safety/boating class is a good idea.
size, depends on what kind of fishing and where.
will you mostly fish in protected areas or want to venture out a little?
If your think about picking up a book or two, I like Chapmans Piloting
http://www.amazon.com/Chapman-Piloti.../dp/0688148921
might help you get a better idea of what you want too.
always take the boat you are thinking about for a sea trial... you want to know is sea worthiness before you drop the cash....and remember, the initial investment is just the beginning of $$$$