"SyntaxHighlighter TinyMCE Button" provides buttons for Visual Editor and will help to type <pre> tag for SyntaxHighlighter.
A. You need not to select whole your code. It's enough to select first line of your code.
A. "html-scripts" option requires "XML" brush. However, some 'SyntaxHighlighter'-based plugins do not load "XML" brush by default. If you want this optiin, you should consider the use of "WP SyntaxHighlighter".