You have access to a npc server. Just make up a script of some random functions, find out what's the effect of them and read up on object oriented programming in general, it's worth the time if you don't know what a class is or a function.
Edit: I looked through this,
http://en.wikipedia.org/wiki/Object-...ed_programming and it's not what you need.
Basically...
Just remember that classes are libraries of functions so you don't have to retype the same code and they can be joined to level npcs or weapons. I'd also recommend reading fowlplays guide, I thought it was really simple and showed all the basics of gs2 required to produce a script. Just read through it slowly and test the examples to see their effect.