So long as you seek Self-realisation, the Guru is necessary. Guru is the Self. Take Guru to be the real Self, and yourself to be the individual self. The disappearance of this sense of duality is the removal of ignorance. So long as duality persists in you, the Guru is necessary. Because you identify yourself with the body, you think the Guru too is the body. You are not the body, nor is the Guru. You are the Self and so is the Guru. This knowledge is gained by what you call Self-realisation.