Hey Scott, according to their website, if you registered for the Full you can not switch to the Half, but if you still want to I would email the race director or post on their FB page to see what they say.

What I would do is stick to the original plan of running the Full.  If you've put in the training time and your goal is just to finish, then see it through and just enjoy the ride, I promise you it'll be a great one.  OKCMM was my first marathon a few years ago and I'll never regret it.  The medal is awsome, the support is great and it's getting to be one of the biggest marathons in the country right here in our backyard!  That's just my 2 cents, now go run a few miles.  ;o)

why don't you try running a half marathon before the OKCMM the land runners have the bus that goes to Ardmore and that is a pretty nice half, it will help boost your confidence.  Or the Jack Rector Panera 25K that is a good one too.  I would stick with the full at the OKCMM I ran it last year for the first time to ever run a marthon and the conditions were not good but I did it and that is the most important part.  Make your goal to finish it and you will be fine. 

I think the half at Draper Is March 18. Strides of March is the name if your interested

I also want to thank everyone for their kind words of encouragement and the ways to go about doing things. The running community is one of the nicest I have ever come across, everyone is so supportive. Thanks.