and how easy/difficult it is will depend on your level of expertise and your pocket.
From what you say it looks as if you already have the video file, is that the case? It must be edited and compressed in one of the video editing software applications like Adobe Premiere. Many professionals use an application called Avid, but this costs around $6500 for the studio version so unless you're in this for a living it's probably not a valid option.
If you have your file (saved as an .avi) you're off to a good start, and now I suggest that you