limonene

Its not difficult. Just spread the training out over 6 months.

MWF, 5 miles each, or about 50 minutes. Run relaxed. You can run slower than walking so long as you're still running. The idea in the beginning is to get that aerobic capacity. Walking in the beginning is ok, after a month or two, you'll be able to do the whole 5 mi. w/o stopping.

Then on Sat or Sun, do your long run. This starts as your longest run. Say, 5 mi. And it is sloooowww. Easy.
Every week, add 1 mile to your long run, or 10 min, whichever comes first. When you get to about 12 miles (this is after 2 months, mind you), its a lot, one weekend doing 10, the next 11, then 12; you need to add rest weeks.

So from this point, you add 2 miles to your long run on alternate weekends, and on the ones in between you run half the distance. So your weekend runs would go like 12 mi, 6, 14, 7, 16, 8, till your long run is 22-24.

Then you can run a marathon no problem. And they have them everywhere. I even bet there's one near you in Western Sahara
Here's a link for a training schedule: http://www.jeffgalloway.com/training/time_goal.html#20