what does it take to swim big distance?

I have been swimming for some time now. I usually do about 4000 yards four days per week. I have never done a long distance swim. I'm not sure why but I have been tossing the idea around in my head to swim a 30-38 mile Fresh water swim at the end of August. I'm not concerned about the time it takes. I'm thinking I would need a support crew, nutrition while underway, lights etc. etc. I would appreciate any feedback and insight you could lend regarding workouts to build up, experiences, recommended suit, food, etc. etc. Lets hear it.