Regarding file transfers. As far as I know the device you use has to be formatted as FAT32 as the PS3 can't detect NTFS.
Most save files aren't copy protected so you can just copy them manually if you don't want to do a full backup. Some save files which are copy protected can only be moved over to a new system if you do the full backup option with the PS3 and some just won't let you do anything with them at all.
Your PS3 ID can be on upto 5 PS3's I think, but make sure you deactivate it, as Sony can be a bit difficult about them doing it for you afterwards.