I Can Run the NYC Marathon?!????

Let's say you entered a lottery on a whim to run with a great nonprofit but have never run more than a half marathon. Then you get picked. But twenty-six-point-two-miles?!!?! Seriously not sure if I am game enough to sign on a dotted line.
  1. Five halves maaaaybe make a whole
    I've run five half marathons in the past nine years
  2. Just keep putting one foot in front of the other
  3. I did the great saunter in 2007, where you walk around the perimeter of Manhattan. Same difference?
  4. Yolo
  5. Other ideas? Motivation? Or should I just stick with the usual couple miles instead?