To be completely honest, it's only as difficult as you make it. If you want to go no contact, the steps easy enough to do. Block their calls, avoid them at all costs. It might be more difficult emotionally, which is why it's up to you how difficult it will be.
Setting up boundaries is all fine and good, IF you are willing to stick to them. If one of your boundaries is to not talk to him if he's drunk, it's up to YOU to make that happen. Don't expect the alcoholic to keep your boundaries. Boundaries are for you.