I won't lie, we all feel nervous. Even the hardest core, most decorated veterans of conventions feel a little twinge of nervousness when they show up to the convention doors, not knowing how they'll be received, how the convention will look, what surprises will be in store...
And that's half the fun! I've never shown up to a convention expecting what eventually occurred, it's a different experience every year. The best thing about this place is, you already know people will be at least decently receptive; they're at a convention for something you already like.
That being said, look around these forums and take all the advice you can. The more prepared you are, the better your first experience will be.