Am I insane....?

I was talking to my father this evening about Rachael's Run. Other than my hubby running ahead of me again, I had a great time.... a REALLY great time. I like running... even though I'm not so great at it. I told him that I was looking forward to doing another 5K this weekend and then an 8K on Thanksgiving Day. To which he responded, "Are you training for a marathon?" I laughed it off and told him that I was barely finishing 5K's at this point and a marathon is a little outside of my goal range. Then I got off the phone and really began to think about it.... Could I really do that? Sure, I'm not in shape for it now, but could I be? Do I have that kind of motivation? I started looking up how to train for a marathon online. The first four weeks include a series of 3-4 mile runs with a once per week 'long run' of 5-9 miles.... It goes up each week after from there. It's definitely something to consider.... we'll see.