If you feel that doing a marathon is a goal you'd like to achieve then I say go for it. It is a lot of pounding though. I've done a couple and marathons just aren't for me. I find that I inevitably get injured while training for one! My fave distance is the 1/2 marathon.

At any rate, I don't doubt that you will be able to do it. If you can do the half I don't see why you couldn't do the full as long as you train smart.

Good luck!