If you have the time and the patience to research the current regulations, and the confidence to navigate a tricky bureaucracy, then you might be able to represent yourself in a hearing.
Because many people lack the time to research, however, it's usually better for most people to hire an advocate or attorney who is familiar with the agency regulations. A neutral third party who understands the system and has worked with the agency before can protect your interests effectively. Also, since even a single misstatement could count as an admission, it's usually safer if someone other than the business owner talks to the agency during the investigation phase. The money spent protecting yourself from losing your business and your ability to practice in your profession is small compared to the financial costs of a negative state action.