...You update through iTunes with the original firmware, then change to the Rockbox firmware. Now your music is updated in Apple firmware and Rockbox firmware.
And actually you could just use the Rockbox installer...it does all the work for you.
heres the link:
Rockbox Installation Guide
If you go to a link on that page, there is another installer that installs both Rockbox and iPodLinux.
As of now, the Rockbox Installer Project in iPodWizard is discontinued...I would have gone there for an installer but it is no more.
