Another thing I can recommend above the DVDs is the audio tape by Bob Jacklin & Gary LaFontaine called "Fly Fishing the Upper Yellowstone in Yellowstone Park" (get it here
[url=http://www.thebookmailer.com/Tapes/Audio/audio.html:c945e]http://www.thebookmailer.com/Tapes/Audio/audio.html[/url:c945e] .)

Listen to it in your car everyday before your trip!