Adjust CSS using javascript rewrite so that horizontal menu appears properly on website

I have a website with a CSS/JS horizontal menu: [login to view URL] It works well. However, we have a custom content management system I need to use and it will only generate HTML for the navigation like this: [login to view URL] If you look at the code, you'll notice that the CSS classes are different for the navigation. The CMS controls this when it outputs the code, so I can't change it. What I need for you to do is create JS code to go in the header of the HTML of the template at [login to view URL] that will rewrite the classes in the HTML so that the navigation will appear as in [login to view URL] in all aspects, including the responsiveness of the site. You will not have FTP access, but you can grab all code (including external JS/CSS) files from the site. When you have it fixed, you can upload it somewhere to show me the solution. Thanks!