Find on this Page is very easy. All you have to do is press command-F, or go to Edit: Find.
As for address bar searching, my favorite plugin is Keywurl. You can configure it to search just about anything, including I'm Feeling Lucky. In fact, that's one of its example demos. Go to Google, control-click in the search box, and select "Create Keyword". Use default as the keyword and set I'm Feeling Lucky as the button to invoke.
My only problem with Keywurl is that it seems to always be a version behind the current release of Safari. I hope it gets re-released as an "Extension," which is a more well-refined system of plugins.
