CMS programs typically use a storage system of some kind tied to a script:template system.
If your current site is strictly page-driven, then you'll need some way to get that content into the CMS storage so the script:template combination can access it. CMS that use "flat file" storage may allow you to do some fancy copy-and-pasting to get your content into them.
If your content is database-driven, then you'll probably be able to devise a way to dump that info into your new CMS structure, as long as it also uses a database for storage.
Other than that, it's not too tough to grab a CMS like
Joomla and spend a weekend creating pages in the CMS and copy-and-pasting-and-tweaking your existing content into it. While it's almost like manual labor (!), it goes pretty quickly.
Most likely the biggest issue for you will be designing/modifying the template system to get the look you want. Plan on spending at least a day or two to get that done. Or more, if you're not used to working with often-unusual CMS syntax. I can assure you that making an exact duplicate in a CMS of a unique site, particularly one with lots of cool dynamic features, is a pretty big challenge for even expert coders.
Bookmark their support forum!
