Nobody should ever plead guilty at their first court appearance on charges as serious as this (if on any charge). If a grand jury has met and has issued an indictment against him, he will be called upon to enter a plea. That plea should be not guilty. If the alleged conduct is fairly recent and an indictment has not yet issued, he won't be called upon to enter a plea at all.
The Justice will simply explain that the case must be presented to a grand jury before it can proceed, bail will be established, continued or modified, and he'll be given a date to return to court. By that court appearance, the grand jury will probably have issued an indictment, and he will be arraigned on the charge and will enter a plea of not guilty. Once he is arraigned, the clock will begin ticking toward his trial date. He clearly should get an attorney on board immediately.