Hey, I've got a new imageboard up currently running on Kusaba and since Kusaba isn't supported anymore I need to upgrade the software to Wakaba and don't know how to start. Can anyone help me?

Try upgrading to Serissa: www.serissa.org.

surely someone can reverse engineer the wakaba-to-kusaba converter.

just install wakaba. i'd bet money that your new board isn't active enough to have very many posts yet, and if it is the posts on it now would probably be gone in a couple days anyway.