Congrats on your recent puchase!
I will answer your last 2 questions first, as the solution there is somewhat simpler. If you have a video that is half-side-by-side or top-and-bottom (aka over/under), you can play that video with any of your normal media software at full screen. You would then use your remote for the TV and set it to the appropriate 3D mode for the video.
There are media players that will also output row-interleaved 3D without the requirement of 3D drivers, such as Stereoscopic Player, Cyberlink PowerDVD, KMPlayer, etc. When output in this format, the signal to your TV is a normal 2D signal, however the passive polarized display will be in 3D. Youtube has this function as well. You can also use view row-interleaved images as you would any pic and can even have them as your desktop background.
AS far as drivers go, I am assuming you have a reasonable Nvidia graphics card and updated drivers. Nvidia's 3D Vision / 3D Vision 2 kit is meant for approved 120Hz monitors only, so they will definitely NOT work with a passive 3D TV. Nvidia's driver option for 3DTVs is called 3DTV Play, which will output a 720p60Hz or a 1080p24Hz framepacked signal using HDMI 1.4. Unfortunately, your TV is not on the compatability list, so it will not work unless you do an EDID override. The only benefit to having a 3D Vision kit is that the emitter is detected by the driver and allows you to activate it without paying a $40 fee. Personally, I think foregoing 3DTV Play for the new "Optimized for Geforce" option is the better route.
If you want to try 3DTV Play, you can follow the directions here:viewtopic.php?f=105&t=13176
The 3D Vision drivers now directly support specific passive displays that are "Optimized for Geforce." The main drawback to this method is that you are only able to render at the native resolution of the display, which is likely 1080p. If your card is not capable of playing modern games in 3D at 1080p60hz, this may be an issue for you. Being an LG, there may be a couple of other issues as well, including colorbug and eye swap issues.
You can find more info here:viewtopic.php?f=115&t=13821http://3dvision-blog.com/7163-make-your ... 3d-vision/
Yet another option would be to use 3rd party drivers such as Iz3D or Tridef. You need to pay to activate these as well, however they do come with free trials.