Definitely ask to be represented by a Public Defender. Ask if you can have Petty Theft, which is a Misdemeanor reduced to an infraction. You have no prior arrests and agree to pay fines. Expect the worst, hope for the best. Learn from this and go on with your life.
The answer by pehunt pretty well summed up your situation ! Generally, after a year or two with no other offenses, you can apply to the court to have this item expunged from your permanent record , an attorney can advise you further.
You'll probably b charged with theft, pay some fines or community service r both, if its first offense that's good. You can take classes I believe ARD class, upon completion I think they erase your record. I know a guy who stole thousands from Walmart as an employee and a woman who stole over $30,000 from kids football org as the treasurer and both cases they took classes and now have no record.