I was trying to quote from candy, agreeing with a specific point he made; but my laptop is dying....
so, my take..
virtually anyone can do it.....
BUT, big respect for the distance and the day.
I think that from the beginning, you have to identify where you personally are at and train accordingly. Apart from a broken ankle, I was pretty fit, I was a competative gymnast from age 6... and competed in many other sports.... SO
I had a good base endurance background.. and still found it VERY tough.. OK, on the day, I was a bit floored by stomach problems... but......
if you are starting from a very low point, appreciate that, ask for help... it will come tenfold from the forum.
There is no escape from putting in the training and the time.....
Don't be scared, just be prepared!
(If Hallmark cards come running I've got the copyright on that sentence innit!)
(disclaimer, said with 4 pints of Stella and a bleeding ankle! : )