Welcome to the site Adam :cool:
First, sit down and take a deep breath, there is lots of time left. Unlike Tennis or Gymnastics (where you peak at 14), dirtbikes are a lifetime learning experience. Malcolm Smith (the most famous off road enthusiast in the sport) is 63 years young and is capable of far out riding many folks far younger than his age. At eighteen, you have many years of learning and fun ahead of you.
I thought at first (reading the title) I would move your post to another forum to answer your question. After reading your entire post, I realized that would be a mistake. Instead of that, I would suggest that you grab a tall glass of your favorite beverage and become one with search. See it up there in the bar just under the banner? Search can be your friend. There is tons of information buried within the annals of DirtRider.Net. Search is your friend that can wade through the compendium of knowledge we affectionately call DRN and bring it to your screen.
Once you begin to learn, many new questions will present themselves to you. Search for them as well. As questions arise that have no apparent answer, post them up and start a new discussion, thereby adding to the vast knowledge within.
You know, some days I think I should change my screen name to Yoda. ;)
Back to reality, be sure and go to your User CP and update all your information. We will do our best to hook you up with some fellow dirt bike enthusiasts. This is the best darn dirtbike website around and we have the finest folks in cyberspace ready and willing to help a newbie willing to listen and pounce on a fake.
Some of the best folks hardly leave their local forums, so be sure and check out the local forums for sure.
Again, welcome to the site, and shout if you have any questions!