i haven't had the kind of surgery you are having, but i have had three surgeries for other health problems so I wanted to jump in. Hopefully someone who has had the same procedures you are having can jump in with more details for you.
It's totally normal to be nervous. Surgery of any kind is scary.
Going under anesthesia is really easy. The doctor gives you something to just relax first and then you just drift off to sleep. Nothing to it. When you wake up you will be disoriented and groggy. A nurse will be there who will be talking to you as you begin to wake up. You probably won't feel a lot of pain at your surgery site yet because of the anesthesia and the local anesthetics injected into the area. Before you are allowed to go home, all of your care instructions, (including prescriptions) will be explained to you and to whomever accompanied you to yor surgery.
The pain in the days following surgery really varies by person, but you will be given painkillers and instructions on how and when to take them. It's better to keep ahead of the pain than it is to try to calm pain down, so follow the instructions of your doctor. Some painkillers can be constipating, as can the anesthesia fom the surgery, so be sure to ask before your surgery about using something like Miralax to prevent constipation.
Because you are so young your rate of healing should be pretty quick. As you heal, the pain will go through different stages, and some days will feel worse than others.
Just make sure you follow all the instructions of your doctor so that your healing will go as easily as possible.
Most importantly, you matter. You matter a lot. And you are taking a very brave step toward getting better. I know it's really hard not to worry. There isn't really any way to completely get rid of the nerves before surgery. Just spend some time doing the things that you find most relaxing and fun...t.v., reading, music, computer, video games.
You're going to do great and this whole ordeal is going to be over soon. The one thing that makes the pain of recovery from surgery slightly easier to tolerate is that you know the pain is taking you in the direction of healing. Just keep telling yourself that.
And sooner than you know you're going to be back doing everything you want to be able to do again.
Good luck with your surgery, and please keep us posted, ok?