Just found this thread - might have gone cold by now though! Anyway, great race if a bit tough - first time for me, but I'll be back! I also found the traffic from Grange onwards intimidating, I'm surprised no-one has been hurt, it's a bad road at the best of times. To add to the timing debate - my official time was only 15s different from my watch.
I was a 40+ ciggy smoker 4 years ago and took up running to help motivate my umpteenth attempt at stopping. I signed up to the GNR and haven't looked back since. Don't want to go near another fag again!
As for the booze - well, it hasn't stopped me either, but when I have the occasional period of abstinence (sometimes a few weeks at a time) I go for a run instead of the bar. Works everytime!!
Good luck and stick with it - I'm sure it's not entirely in the mind, but a lot is.