Remastering Knoppix in Knoppix on an existing Linx partition

I've got a (semi) complete Gentoo installation on my computer, but I'm having trouble with it and internet access, so I've been using Knoppix for most of my comp work. I'd like to customize it some (change background, some settings, ect), and was wondering if I could do so through Knoppix itself, using the existing reiserfs/ext3fs file systems as a basis for the build. I was thinking something along the lines of /home/user/knoppix for root, and then go from there. Anyone got any ideaS?