Hi
Assuming that you have no history of injury or a medical condition that could cause a problem, my advice (which many may disagree with) would be "do it".
I would recommend running long every weekend up to the race (which again many may disagree with). Don't run at all in the three days leading up to the event.
Make sure that you kit is in good shape - shoes should be comfy, proven, and have less than 300 miles wear. If they are your old school pumps, bin now and get fitted into a fantastic new pair instead.
On the day, adopt a strategy of run / walk. Run a mile, walk for one minute, run the rest of the mile etc. If you can't bear that proven strategy, drop to a very slow jog for a minute each mile instead.
Remember these things well - Hydration is important, drink enough water before, during and after the event. Pace is important - start very slowly. Belief is all important - have confidence that you will be able to complete, create a mental picture of you completing and rehearse that picture 1000 times before you run it.
My apologies to the coaches that may consider my advice a little cavalier! It is a crazy plan, but "it just might work".
Good luck
Gavin