Umm why do this the next race? Why not in two years? It's a much safer time frame and that's a lot of miles for less than a year. An awful lot. There is not one expert in this area that would suggest someone go from no running at all in March to a full marathon the following winter, not one. I am not saying put it off forever, I am urging caution and safety. There are many wonderful running clubs out there and groups that would give you the same advice.
While I believe in walking breaks ala Galloway, I just think this is awful fast. I have been running a number of years now and am a certified personal trainer (ISSA not currently working because of the kids) and just would urge some serious caution here. This is not a 5K. This is 26.2 very long miles.
I am not, in any way, trying to dissaude the OP. I heard this a lot when I started running and wanted to go out and do a marathon my first year but the people urging me to be safe and take it a little at a time were right. I overtrained and got pneumonia. It happens all the time. It laid me up for months. Not weeks, months. Will this happen to everyone? No, not at all. It does happen tho. The OP has no base at all. None. Not a few miles a week, just no base at all. What's wrong with building a base for a year, getting some short races under their belt and trying before they attack a marathon? You get fabulous support and encourgagement in local shorter races too. I run a 10 mile race every summer (CRIM) that I would put up against most marathons for crowd support and sense of accomplishment.
A marathon is a fablous goal and if you run or want to run you will think about doing it. I am just saying it is a big bite to chew for the first year. I support and encourage the OP. I believe running and walking can change your life 100% I am living proof of that. I just want people to have some caution as well.