1) The directories are designed to be used for various bits of code. In general, Layout is for subtemplates and Includes is for code snippets that can be included in other templates.
2) Yes, that should work, depending on how the template is set up.
3) It depends. If the text is embedded on the image, you'll need to clean that up. If it's set up through a menu controller, then you'll need to edit the menu control and possibly the page names.