Hi Sam-
In terms of reading material: I recommend a book called “Audio In Media” by Stanley R. Alten, available at amazon.com. It’s actually a textbook and is a great starting point for all-things-audio including voiceover techniques.
As far as mics, the RE20 is $399 at B&H, the same price (I think) as the USB2200a you were looking at. Though I have not used a USB mic, I’m very wary of them. Some things about them may be as good as the more expensive condensers (like the freq. range), but other things (like siginal-to-noise) may not. Like photography equipment, you get what you pay for.
In regards to your project, keep it simple. Watch the video with or without the talent as many times as you need to. Then write a script for the talent to read based on a rough timing of the video clip you need to have vo for. Then put it together in editing.
Hope this helps…
Regards,
Dave