If an infraction doesn't happen and you are convicted of a misdemeanor, you will have some problem. First, because theft is a moral turpitude crime, it is possible that your citizenship will be denied. You should consult with an immigration specialist to confirm this.
As for erasing the record, it is almost impossible to erase the arrest record, however, it is possible to expunge the conviction, if you are indeed convicted. Please note, an expungement will only hide the conviction from private employers and not public employer like the government.