Well, one can eat what they want, but if they want to change their lifestyle, better earlier than late. One should eat to live and not live to eat.
But a good thing is that you have decided to change your eating habits. Post fast diet is very important and sticking to it. Many fast for cleaning and go back to the very same diet that fit them sick.
I would say that one month of raw plant based diet would be a good enough time to fast relatively successfully and with fewer symptoms of detoxing.