Comment 30 for bug 658042

1.) Which ISO should I customize? ubuntu-13.04-desktop-i386 ?

Are there any detailed instructions to replacing the kernel?
I followed https://help.ubuntu.com/community/LiveCDCustomization?highlight=%28livecd%29#Live_CD_Kernel
but got a non-booting image. (it bootsm but later on it reports : mounting aufs on /root failed: No such device

Can I just replace the two files vmlinuz and initrd.lz?
If yes, where do I get the initrd file?
If no, what are correct steps?