First of all, I would recommend searching the forum for training tips that some of the other Peak Veterans have provided. I think one of the best ones I've seen is max the incline on your treadmill and just keep walking until you can't stand it anymore.
Next, if you are a 5 hour marathoner you will probably be doing very little "running" during the ascent. The first half mile is relatively flat, then it just gets steep, you will probably be walking the next 4 miles with rocks and tree roots waiting to trip you up. After that there are several sections that are moderately level that you may be able to run, and leading into Barr Camp there are actually some downhill sections (again all with rocks and tree roots). After Barr Camp (about 1/2 way to the top) you will most likely be walking the whole way up to the summit.
The biggest thing I would caution against is oxygen deprivation. DO NOT go out too fast at the beginning, you should probably hang out about mid pack with your wave and adjust accordingly to how you feel during the first few miles. The wave seeding is actually pretty accurate so trust it as a newbie.
The altitude affects everyone differently and above A-frame (tree line) the oxygen level decreases quite a bit. You want to pay attention to your body, many people turn into zombies the last 3 miles and it's not pretty. If you can, get out here before the race and get to the top by hiking (an easy ascent) or driving, hang out up there for a couple hours, and see how the altitude affects you. Caution: even the altitude at the start line causes some flatlanders problems...
Lastly, during the race be sure to stay very well hydrated, the aid station support is awesome! use them along the way.
Good Luck in August!