Snowsong is right about making your character. What I would recommend is think about basic D&D and what you would enjoy playing there. Don't worry about actually making your character, just concentrate on the concept. Once you have that, then start looking at the book and such. Just bare in mind though, can you physically pull off what your wishing to do (ie, can you really sneak, can you disable a trap/pick a lock or learn to, can you throw accurately). Remember that anything you want to do in this game, you will have to physically do it. Granted though, there are several players who will be more then willing to help teach you. If you have never picked a lock before, but you really want to play that sneaky guy, not to worry, someone can show you the ropes.
Just a quick side note, please plot, put in more Legerdemain moments, lets make that skill well worth it!
Anyways, the point I am making is think about what you both want to play, and think that you ultimately could play.
Lastly, when considering to NPC or PC your first event. Both are a lot of fun. Don't be discouraged because you don't know the rules. There is nothing quite like being thrown into the middle of it and trying to muddle your way though. You got to sit down and talk with other PCs and watch as the new character you made grows. You'll form bonds and be faced with difficult choices. You may even die. The world is a hard place for a new PC, but those bonds you had made will only strenthen. Plus its free your first time.
On the other hand, it can also suck when you have to sit on the side lines for a weekend. You'll do things, trust me, but you wont be in the thick of it. As an NPC, your on the front lines all the time. You get your weapon, you get your character information, and you charge in with gusto to take out as many PCs as you can! And then you die... And then you charge back in! Its fast paced and gets the heart pumping. As a new PC you're afraid, as an NPC you're all guts! (though those guts are often on the ground).
Ether way you'll make mistakes and you will learn the rules.