Well glad your putting yourself out there. It does take guts. I mean most people would never step out of their comfy box. I give you big kudos for that.
Sounds like you are a survivor? no??
Well FWIW I am also a 2 time cancer survivor. I ran my 3rd marathon in 02 while still in recovery and grossly over weight from the depression I had sunk into. Most cancer patients lose weight- I gained it! UGH!
Anyway, have a good race and have fun. You will do great! It's amazing what our bodies can do when our mind lets us!