My first thought would be to take the animation, if you created it, and apply an alpha channel to it(quicktime compression, animation, millions of colors +). Then, when importing into 844, select use fiile's alpha, straight alpha under the import option. If this is something you can't do, you can select multiply for the blend mode of your clip to eliminate the black. Then, for eliminating color, you could try doing chroma keys or luma keys depending on what colors you need to get rid of. Also, if the text is static, you could create alpha mattes for it. If it is animated that will be a bit more tricky. Let me know if any of this pointed you in the right direction.
Not a problem. You can get some very interesting looks by toying with the blend modes. It is similar to photoshop. One of my favorite techniques is to duplicate the video layer and then adjust the top layer's blend mode to give it different looks. If it is too strong you can always adjust the opacity or even throw on an xblur to spice it up.