i really need help with skinning basics on xion

Hi eveyrone, most of you probably know me from wincustomize. I got major problems with even beginning to skin xion.
first question." I know it has to be psd format, but when i make the skin in ps, does the WHOLE skin have to be a continous of play button, background..ect.... what if i need 3 layers to make the background? then what? Do i save it as background then reopen it and start on the buttons? and what if i need a few layers to make a button? this is where i am LOST. Alot of my work consists of more than one layer, so i have no idea how you guys can make these skins and yet have them in one psd file .....
im dying to make xion skins, so please explain in laymens terms if possible. thanks.
first question." I know it has to be psd format, but when i make the skin in ps, does the WHOLE skin have to be a continous of play button, background..ect.... what if i need 3 layers to make the background? then what? Do i save it as background then reopen it and start on the buttons? and what if i need a few layers to make a button? this is where i am LOST. Alot of my work consists of more than one layer, so i have no idea how you guys can make these skins and yet have them in one psd file .....
im dying to make xion skins, so please explain in laymens terms if possible. thanks.