Welcome to the xx world dmorris. As for aftermarket parts and such, look around and you will be very happy. I would probably suggest the 13t sprocket for your first mod. Its cheap and very effective. Around 10 to 20 bucks depending on where you get it. It adds a lot of low end torque and eliminates some clutch work needed for the tight trails. Congrats on the purchase and hope you enjoy the site.
Welcome. The Big 3 is always a great start (air filter, Exhaust, EFI Module). In my opinion either get a full exhaust or a slip-on that you can later add the header to. This is one thing I regret. I love my slip-on but I really wish I would have gone the route of FMF so I could add the Powerbomb header. As far as air filter goes, if you are going foam the Uni is great. For a paper filter Velocity seems to be a big hit. Finally, the power commander is the best EFI module out there but others work as well.