You can put linux if you want, but all you'd be getting are a few games, which I think are better in RockBox. As long as you follow the guide EXACTLY, then there shouldn't be any problems. ;-)
LOL It's up to you, really. Both guides show what are the advantages of having it, so just use your preference to chose which. ;-)
for ipodlinux manager it will install ipod linux on your ipod the link is right here Open it extract the files into a file and click ipod linux mangager.bat with your ipod plugged in and follow on screen instructions.