Yes, you need a lawyer. If you can not afford one you will have opportunity to request a lawyer be appointed to represent you for free when you appear in court.
Your lawyer will advise you how to plea, but I will tell you that you certainly do not want to admit guilt.
Whether the charge remains on your record depends on a few things. If you are under 18 it is possible it might automatically be cleared after a period of time. If you are over 18 you would have to petition the court to have the record expunged.
It is possible that with a lawyer's help you can get this resolved with no criminal record.