I don't know the differences between a standard 500 and 590, but from what I understand the 500 is the basic shotgun while the 590 is more "tactical".
I highly suggest going to a 3-gun event. You will be surprised how challenging it is, and how much you will learn; not only with your shotgun but also with your pistol and rifle.
I just went to my first 3-gun match and i'm positively hooked! Before going to the event I didn't even know how to manipulate or load a shotgun. After one event, I can load, shoot, manipulate, and hit all my targets -- both strong side and weakside
For example, the 3-gun stages challenged you to shoot your guns both strong/weakside, different positions(sitting, standing, moving, prone, from cover), reloading, and shooting different kinds of targets (clay, steel, paper, etc).