Al: As folks have mentioned, yes one can complete a marathon without significant mileage training. I've run a marathon each of the past 4 years without running more than 5 miles, 3-4 days per week.
Blend some modest running, crossfit Metcom work, and basic strength and you can gut it out. Just plod along at a slow pace, stay well hydrated, and refuel with some energy sources along the way. You'll be really miserable during the 2nd half, but can be proud of the accomplishment when finished.