I won't say that it's crazy and it certainly is doable to make your first race a marathon... but for what it's worth: running a couple of shorter events, like a 10K or a HM would help with what to expect on marathon day. You'll get a feeling for what a start is like, hydration stations, and the general buzz of an event. Granted, a marathon event is something to behold, but from personal experience, I found that having run other events prior to my first marathon helped me tremendously. You will be able to find events that fit into your training plan... But even if you don't, you will do fine - but you might enjoy your marathon more with a bit of event experience.
Best of luck!
-bill