Marathon?

So, I have been thinking... I might want to do the PF Chang's Rock N Roll 1/2 marathon... But I am not sure I can train for it in only 3 months! And its kind of expensive, so I wouldnt want to sign up for it and then not actually do it. Maybe I should just train like I was going to do it and do another one some other time. I am sure there are lots of marathon's around that I could do. I just was thinking maybe if I had a goal to achieve that was more permanent than just one I make up it would motivate me more to get out there. I don't know, I have never been a runner but it might be good. Maybe I should start with a new pair of running shoes! I have walking shoes, but not running!

anyone done a marathon or a 1/2 before... wanna give me some tips, encouragement, advice, all of the above!?
kk