WordPress.org

Does this plugin work on WordPress version...

Excerpt Editor has been tested on WordPress 2.5 and 2.6

I have ... plugin installed that uses the excerpt, will there be any conflicts/incompatibilities?

No conflicts/incompatibilities have been reported so far.

How do I use the excerpts and how do I display excerpts for Pages?

The use/display of excerpts depends on your theme - more Information. You can replace the full posts with excerpts (either real or auto-generated) by setting the "Replace Posts" options in the plugin.