a class is a very good idea. most shooting ranges will offer classes for beginners. also check
www.nra.org for a list of instructors.
there are classes at all levels, from newbie to advanced tactical classes targeted at law enforcement.
another avenue to improve defensive shooting skills is through IDPA (international defensive pistol association, i think
www.idpa.com) and/or USPSA (united states practical shooting assoc
www.uspsa.org). either of those groups will help you learn to draw from a holster, shoot multiple targets quickly, reload quickly, shoot on the move, use cover, etc. plus it's a lot of fun.
a new shooter will usually do better with a larger handgun because they are heavier and easier to handle. revolvers are typically easier learn with because they are less complicated than semi-automatics.
call the shooting ranges in your area. many of them will let you rent guns for a fee and you can try out some different types to see what feels the best.
if you have a friend that shoots, ask them to take you with them. i have found that most shooters are eager to introduce somebody new to the hobby.