The best option for the "mouseover images for the navigation" is to use a template and on the sidebar to put a Custom HTML widget with this function. Usually whenever I am creating a web site for a client - I go to https://themeforest.net/ (it is not an affiliate link - I just love them :-)) or https://www.elegantthemes.com/ (both sites have excellent documentation!) and I am trying to find the best option possible which means - less work for me. So I would strongly suggest the same - find, replace, play a bit with the design, save your time and take the money! :-) Hope that will help!