In reply to xplorer:
Hi buddy
ND filters are critical IMHO for shooting DSLR style video (they are also useful to put in front of a gopro and force it to use a slower shutter speed at times, e.g hi-speed action/aerial cams etc) video is all about the framerate vs shutter speed, so the use of ND filters on DSLR video is critical to avoid cranking the shutter speed and getting that horrible sharp stuttery look, or avoiding having to use high Fstop numbers (eg shallow dof close up vs pinsharp landscape)
RE: setup, not a nikon guy but in terms of video basics gd rule of thumb is basically frame rate + no more than double for the shutter speed e.g 24fps at 48th of a second shutter, or 50fps at 100th, this looks natural and hence need for ND's..... what ever you do in terms of editing afterwards, unless your running a monster rig or wanting to convert to a intermediate codec, its wise to match cameras so frame rates match (set nikon to the best available video spec of the gopro & match framerates, if you've a gopro black its likely better than the nikon so reverse)
if its just web stuff then 1280p with a higher framerate gives a bit more latitude to play (and for handheld shots) than trying maxing out your res at 1080p but at 30fps which is harder to get steady and smooth (regardless spend a bit on a tidy tripod, the cullman brand on amazon are great value for money btw but if your serious for video then down the line buy a fluid head)
finally dont worry about most of the technical stuff just yet, shoot like a maniac, anything, everything (shoot at the golden hours where possible....seriously in good light anyone can take a gd shot with any camera!!), try when possible to shoot a sequence of actions not just one static image (difference btw the pros and us amateurs I think!) and finally as any aspirant film maker will tell you, sound matters far, far, far more than u think! I can watch crappy phone camera footage but with pro audio feed all day long, but 5mins of stunning 4k with crap audio and its ruined!! the zoom recorders are quite cheap btw
re: books, I wouldn't worry really, heaps of great filming videos on vimeo and youtube, (vimeo film school is great!)
sorry for essay but you did ask! :P