HIM - to race or not to race...

I am reasonably new to Tri. I just did my third event which was the Olympic in NJ. I loved it. I am officially hooked. Especially now that I know I can OWS. I have been training for about half the year only seriously for his even for the past 16-20 weeks. I did okay in the event despite some GI issues which caused me to walk/run the run part, which I was kind of pissed about. But what I learned about this sport is you never know it all. At least for me, I learn something every time. Well I finished the event and have that nagging itch of “what’s next”? I found a half-iron in NJ on 10-4-09. I am wondering if I should attempt to push myself to do that one, even though technically it only give me about 10 more weeks of training. Or should I spend my time training for the Philly Marathon (which I have never done before – in Nov). I thought if I one day had the hope of doing a Full Ironman, it would help if I’ve actually done a Marathon. I’m just curious if anyone thinks I’m nuts to try the Half this soon. If so I can concentrate on the marathon which can only help me for next year. But of course I have the itch. Any feedback would be appreciated. Thanks.