There are infinite forms of run/walking and I would urge you to consider some variant of r/w. They range from 30seconds/30 seconds to running a mile, walking a minute and even longer. The key point of run/walking is to start the interval as soon as you cross the start i.e. do not run 3 miles then start.
I believe running from a longer base going into a marathon is a great idea. Basically, if one is running a longest run every month of 8-10 miles, they are looking to have a huge leg up on other first-time marathoners. So a typical month's long runs may look like 6 miles, 8 miles, 6 miles 10 miles then repeat. Do not get locked in on these as absolute, only an ideal distance.
Look for the Goofy registration to open in early April. The 2014 race opened April 9. Though I would also look at the runD website in February every so often to be sure they do not do something different this year. The marathon registration start has been anywhere from the day after the previous race to April