In reply to climb the peak: sounds like you know what to do and you already do a bit of running which is good. Increasing your mileage gradually and, as others have said some longish runs over similar terrain to the event (i.e. not all on roads if you're training for an off-road event) would be good.
Agree with person who suggested doing shorter but similar events as part of the training. The whole race day routine is easier if you've done it before - you will make less mistakes around prep and nutrition, clothing/footwear, navigation (if applicable to your event) and other things which may ruin the whole thing even if you can handle the mileage.
Very exciting! I don't quite have the circumstances (children, work - boo!) to train for things longer than a marathon, so I'm a little bit jealous. Good luck!