My question involves criminal law for the state of: California

Hello, recently I've been caught shoplifting $30 worth of stuff. I actually got away but returned in fear of a friend of mine who was detained in the store, being the one caught. They gave me a chance to call my parents before the police arrived. I went in the store, and waited until the police came. He asked for my information, age, height, weight, school, etc. The employee also told the cop the story of what happened. Next, I saw a check list of crimes, and he checked off petty theft. He took a picture of the item that I stole, and then my parents arrived and took me home. I was not arrested or handcuffed that night. The cop also said that I would be going to court.

- I have a clean record, this is my first offense.
- Do I plead guilty? Or not guilty?
- My court date is in a couple of weeks. Do I need an attorney? I asked my parents and they said no, saying that I would just be confronting the judge, so I'm not sure what it is. They also said we could not afford one.
- How do I get this off my record? I have good grades, plan on getting a part-time job, and plan on going to college. (I am 16 years old)

Thanks in advanced! Help is much appreciated, this has been on my mind for weeks. I definitely learned my lesson, I ruined my summer.