CRA says: "You can make this disclosure yourself, for free, and you do not have to hire a third party to help you."
If you do that, you are like a lamb to the slaughter. You need to consult a tax lawyer to be sure you know what you are getting into and to protect you from an overly ambitious CRA clerk with a quota to meet. Remember a survey revealed that 30% of the time CRA staff gave the wrong answer to taxpayer questions.
A lawyer cannot be forced to testify against you. Your accountant has no such immunity and could actually be required to testify against you whether he wants to or not.
Back penalties and interest charges owed as a result of natural disasters or severe personal difficulties may be reversed by requesting Taxpayer Relief using CRA form RC4288, Request for Taxpayer Relief.