That is exactly what I did one year ago... sitting on the couch, eating ice cream, watching the biggest loser contestants running a marathon.. I said "I CAN do that!" and what better place for a 1st 1/2 then Disney!
So I started the couch to 5 K program... and slowly worked my way up to a few 5k's, the a 10K and then training for the 1/2
YOU CAN DO IT!!![]()
I was losing weight and walking 2-3 miles a day when I read info in a Prevention magazine about "walking" a half or full marathon. Until that point, I didn't even know that was allowed. I bought a book and started training the next day. 9 1/2 weeks later I completed my first half marathon in 3:37 with me walking the whole thing. Now I'm adding a bit of running and hope to finish a race in June in under 3 hours. You just have to start!

Hmmmmm
tough decision.
OK I AM IN GOOFY #7
On a more serious note; and a do what I say, not what I do note.... I went to the Doc about the Achilles and he put me on the do not run list for a few weeks..... He kind of admonished me for running after the injury became severe. The conversation went along the lines of exectly when did the Achilles start to feel severe.... About Mile 8.... Why didn't you stop..... I though about stopping if it got really bad...... You should have stopped sooner..... I have this streak of races Doc........ We went on for a while but the conversation ended after looking and seeing no calcification at the heel insertion point of the Achilles (i.e. no long term injury) and prescribing a cortisone injection along with a 2 week dose of oral treatment.
I hope things heal quickly! My present from the Marathon was Achilles Tendonitis with a little bit of PF (although I don't feel the PF anymore) and that was the same line of questioning I got, except my pain started at Mile 18, and I did stop and walk (limp). So, the lecture ended there but the look of disapproval did not.
I didn't get a Cortizone shot thankfully - those suckers hurt! But, I hope yours makes a big difference so that you are back to running in no time! 
And after seeing so many others on here that tackled their first full and goofy at the same time, I'm sure I can do it!

Sorry,
Could not contain myself....
Combination new cam and new medal...
Amazing! Very cool!!