One thing I would add to the GREAT advice already given - don't just rehash the entire text review with some extra info added in. The video supplements the text review, so does not need to include info that can be found in the text review. The video is to demonstrate things that can't be explained in words.
Also important is to keep it brief, 3 minutes or less.
Good luck! I'm sure you'll do well, it sounds like you're going to work really hard!
PS - here's a link to the Video Review Content Guidelines, it might help too! link