it really depends on the severity. I know someone almost dying from it (Systemic Candida) and it took him 2 years.
For me it was about 4-5 month. I had moderate Candida.
But: You never get rid of the Candida completely. Candida is a bacteria which is always in your body. Just the overgrowth makes you sick. The goal should be to work back towards the natural balance.
But once you´ve had it you must always take care of not getting it back. People who have Candida are more sensitive for getting it again than other people.
What I want to say is: Even though you might feel at some point, that you got rid of the overgrowth, you never should get back to your old bad eating habits. You will always have to watch out more than other people.
If you eat sweets now and then it´s recommended taking Biotin with it (prevents yeast growing).
But I guess you have to start the Diet first.
As far as I know the leaky gut will improve with good eating habits. It might get worse at first when all the harmful substances come out.
Also an intake of Fishoil could be helpful.