To search within epub, open the file, then press the OK button. (That's the one that looks like a crescent moon, on the far right at the bottom.) It will come up with a menu. Press 7, which is search. A keyboard comes up on the screen, and you just press the number that corresponds with the letter you want, like on a cell phone. It does take a little getting used to, but it's not too bad. When you have the word you want, press OK again. It will underline the first occurrence of the word you've entered. Then just press the 0 key (it has the right arrow on it) and it will take you to the next occurrence, and so on. Once you find the section you want, press the button that looks like a return arrow, just to the left of the OK button, and it will quit searching.
Hope that helps!