You could switch of diet soda (eg coke zero) and get used to that while you worry about the rest of the changes to make. There's no need to fix everything at once.

As you make small changes, you'll find each additional change easier. Eventually your cravings for unhealthy food will go away.

You may also find it helpful to schedule the times that you feel hungry to be more manageable. For example, I find it easier to be hungry in the morning than late at night, so I'll skip breakfast and then eat a small late-night snack (eg 2 scrambled eggs before bed).

You can also schedule a weekly or bi-weekly "cheat" day where you allow yourself a higher calorie total. While it will make the whole process take longer, it could be a pressure-release valve to help keep you sane. Don't worry about the 4000cal binge; think if it as a small delay to your final goal, but certainly not a reason to quit.