There's a Find command, which searches for the word you select, or for Markups, which covers both words (or drawings, etc) you've made with the stylus, or for text you've highlighted. And one of the half-dozen shortcut icons is configurable; you can assign one of a dozen or so functions you'd otherwise access via menu to it, and one of those is "go to next markup".
Ebooks are small, by and large. In IMP format, a 250-page paperback without illustrations translates into a half-megabyte file. Even with a cover and three interior illustrations, a 520-page hardcover is under two megs. So while you won't fit your entire library in the device, you can reasonably expect to fit fifty books, which will probably get you through a long weekend away from a computer to reload.