You'll need cardio shape, strength shape, and power shape.
Plyometrics would take care of strength for awhile and power nature. Might pick one from each section you can do. Every month switch it up.
http://www.exrx.net/Lists/PowerExercises.html
Cardio, go walk hills for as long as the event may be.
When you can jog a little, jog the flats on tops and valleys.
When you can jog more, jog the hill up and walk everything else.
When you can jog even better, sprint the hills.
You can do the cardio 2 x weekly, plyo 2 x weekly. You'll need rest day after the plyo if doing it right. Walking only would be good for blood flow then.
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