Hi Katrina, my daughter is also 17 and a senior in high school this year. She was diagnosed at the beginning of 10th grade. After going through all the meds, we decided on surgery. She just had step 1 (removal of her colon, making a temporary ileostomy, creating the j-pouch) on July 3. She was in remission at the time but knew it was only a matter of time before she flared again and had no other meds to try (or ones that we wanted her to stay on).
She was in the hospital for 6 days. She also had never had surgery or been in a hospital before. It was scary but we were there for her the whole time. Like Cecilia said, you are put under with anesthesia. We went with her until right before they wheeled her in to the operating room. She had a great nurse that knew how scared she was and really helped alot. We saw her when she was in recovery. She looked really out of it from the drugs but she also looked good (OK I'm the mom, she always looks good to me). She was given a button to push to self-admister pain medication. I think it was the first thing they taught her when she woke up. 
She was moved to a room. We decided to request pediatrics, she's more comfortable around kids rather than older, sick adults. And the nurses can be a little more understanding sometimes. For the first 24 hours, she still had the epidural hooked up (that is the way her surgeon prefers to give drugs). She still used her PCA button to self-administer her pain killers. It wasn't unbearable but more uncomfortable. She started walking the day after surgery. She had a hard time walking (some people seem to do better). But she tried a few times a day. Each day she felt better. In the beginning, the nurses emptied her ileostomy bag. An ostomy nurse came in on the last day to teach her (and me) how to change it. It was a little overwhelming at first but we all got used to it.
When she came home, she started going out on small errands with us. She got tired easily. She had a full incision (some people have the surgery done laproscopically). As it healed, the staples hurt. As soon as they were removed (2 weeks after surgery), her incision didn't hurt much. Because it was summer, we didn't push her to get back to doing everything quickly (hey isn't that what summer is for?). She decided, on her own, when we would go to big stores (supermarkets, BJs) to use the motorized scooter the stores provide.
She started hanging out with her friends in the summer. She doesn't like the feel of tucking the bag into her clothes so she bought several baby doll type shirts. She just made sure they were the longer ones. I know many people here wear fitted clothes with ease. She goes to movies, plays her musical instruments, went back to work. She does participate in gym.
She is scheduled for her step 2 surgery on November 10. She could have it anytime after the beginning of October (3 months after step 1) but wanted to try to fit it in to her school schedule. She missed alot of school the past 2 years and wants to enjoy as much of senior year as possible. Since she was in remission when she had her surgery, she can't say she feels better since her surgery. But she knows she won't have to worry about flaring ever again! And that makes her happy. And she is on no meds!
It's really important to have a good support system for you. Family support will help alot. We didn't even know what UC was before she was diagnosed. Educating yourself (and your parents learning as much as possible about what you are going through) is important. I also asked the surgeon to speak to one of his former patients who had been through the same surgery. I wanted to talk to someone who had been about my daughter's age when it was done. I spoke with a great girl who was diagnosed at 16, had surgery at 19, and is now 22. That also set my mind at ease. I did more research than my daughter. She didn't even want to see an ostomy before her surgery. The surgeon and the nurses all said that was fine. And it was.
Being scared is normal. But looking towards the final result (a happy, healthy body) is the goal. My daughter knows that it may take up to another year for her new pouch to really become "normal". And normal after surgery will be different than normal before. Just a new normal. Also ask the surgeon to go through the surgery and recovery process step by step. The unknown can make things even scarier.
You can also go to j-pouch.org. They are also a great support forum. I have heard of Dr. Fazio from this forum and j-pouch.org. It seems he is a great surgeon.
My daughter's screen name is bratcat. She comes on once in awhile but if you ever need to talk, I am sure she would be more than happy.
Don't hesitate to ask more questions if you have them. And maybe your parents will want to read some of these posts (and maybe ask questions too).