documentary = TV/Movie = 1080p = 2mb. 4k video (which is actually width of the screen now 4096 x 2160 pixels) is shy of 9mb. You will have more than enough resolution.
Outside of that I would go with the D800 - who knows if the D600 "spots" will be fixed. For doing that trip, why not. A bit better made and more resolution for crops as well. That can save a long lens for sure.
Lenses... I would stay away from any that are not internal zooms (i.e. lens expands in length) as much as you can.
70-200vr, 24-70mm, 16-35vr - For durability - no brainer.
2x or 1.7x TCs.
50mm f/1.8. Always have to take a 50mm.
24mm is wide on FX and there, I'm willing it will be more than wide enough. In the midwest we have land where you can see for 70-80 miles on a good day from a high point. Super wide angles can get to be too much. 24mm is about as wide as I like going. Depends on taste and what you are grabbing. I think I would just take my Tokina 17mm & 15mm fisheye can call it good for a super wide. Those two with the 24-70 would give one everything and with a D800 you can crop what you don't need.
For Hardrives, I would go a used net book with 2 500gb drives. Use one for back up.
Power - you might look at Goal Zero (Goal Zero - Escape 150 Adventure Kit is one I have been looking at picking up.) I have seen them used by quite a few people. Brunton are good as well.
Filters - 3-4 stop grad or split filter to bring the skies back.
Tripod - lightest you can find.
Pack - I use a Lowepro DryZone Rover Backpack and you can get all of the lenses and photo gear in there that I put above. It can hold a ton and is still comfortable to carry. Heavy pack but waterproof, has a water bladder, and mine has take'n the worst I have thrown at it. I plop it down in mud puddles without hesitation other than to keep mud off my backside.