how to switch from one firmware to another 30gIPod

[stevio]

just installed rock box and doom but cant play music any more after installing doom every time i try to play something it says (root)? twice
one on top of the other. Rock box played music from itunes and worked find when i first
used it. now it wont sync with itunes , sync bar is empty but itunes is full of
of music maybe theres something i dont know i want to be able to put music play music as well as have rock box to i know theres got to be a way around this i dont care about itunes is there a other better music software?

PS- i am very new at this and dont know to much about rockbox or ipod hacks and such
but wish to use this firmware its very cool