I’m not an attorney, but your

I’m not an attorney, but your statement that “We know that we can use any video we can find online because of fair use law” is pretty far off the mark. If you’re doing interviews on a college server, and none of what you do goes out on the web, you may be o.k. in your assumption. However, if your series is to go public I’d be very careful, as both You Tube and Vimeo make take down your materials.
I suggest you look at a document produced for students at Stanford University by the Stanford Library, and follow the several links on this page. There is quite a lengthy and enlightening discussion of the subject here. (http://fairuse.stanford.edu/overview/fair-use/)
If the material you’re using does fall under “fair use” you won’t need to obtain permission to use it, or contact the copyright holder. However, credits at the end of each segment, acknowledging the sources, would be a good idea, just as you would if you were quoting sources in a term paper.