I Chose My First 50k Race!

Omg y'all, I have chosen my first 50k race!
After contacting Mainly Marathons and finding out that Connecticut would be at the end of June in 2018, I have chosen Delaware as my first 50k!
It will be on May 8, with a much better chance of having good weather.
I found a training plan online and it's already written into my planner. That's just how I roll!
Ok Ultra Runners.... any books I should read, gear that I need? This will be less than a 2 mile loop, so I will probably not need a hydration backpack, which is nice.
I cannot believe I am doing this! I am dying to register and make it officially official, but registration isn't open yet.

What's the longest distance you've run?