Should I get an expungment?

I was arrested as a juvenile and charged with a disorderly persons theft. I am now 19, and was just arrested again for credit card theft 3rd degree. I am completely ashamed and embarred. The police said it will most likely be knocked down to another disorderly persons theft. However, it will remains on my record as I'm now an adult. I attend school for Criminal Justice and hope to one day work in law enforcement. Hopefully in the prosecutors office. Should I get an expungment? I was told yes and no. I was told not to becasue it will show up I have an expungmenet and there is no way to prove what it was for. Either way, will this hurt my chances at a career in the field?