Navigation Bars – JS/CSS Mega-Drop Downs

Hi, I’m a Designer that is new to WP. I’m used to working in HTML/CSS. How can I install and/or build a custom JS or CSS Mega-Drop-Down navigation bar? It needs to have an ‘active’ or ‘current’ page indicator. And, it has to be editable through an ‘include’ or similar device, so I don’t have to manually modify the code, on every page? Is there a plug-in for this? Also, I don’t want the Bloggers/Admins to be able to modify any of the navigation via the WP interface.