Text translation, a menu question and image sizes.

1) I am starting a site in English with French content, I would like to know where I can access the text for "next post" "previous post" and "continue reading" I would like to translate it to French. 2) On the scapeshot pro theme demo there is text displayed to the right of the full screen menu, how do I set this up? 3) Are there a list of recommended images sizes for specific uses? Thanks