Gentoo is a beast, I've been running it off and on for a while and it's pretty daunting. You have to get used to compiling kernel, especially if a new version comes out every so often. I'd get a spare computer and install gentoo to it, running in VirtualBox will work and there are some kernel .config people put out just to run gentoo as a guest in VirtualBox to make it a bit easier, but there's a distro called Redcore LInux that works out of the box with VirtualBox. Give that distro a try and see what you think.

www.redcorelinux.org