IDE and ATA are the same...
IDE is the bustype, and the kind of ATA used means if its an 33/66/100/133mhz speed
SCSI and SATA are different from this... because they use other connectors, SATA is standard on G5, and SCSI is an option in all of them, and there are different types of SCSI with different type of connectors...
so just buy any type of 100/133 IDE ATA drive and it will fit in your G4
as mentioned, no cables required because they're allready built-in
maybe some screws, but I think you get those with the drive...
and then setup and format the drive with the drive utility in MacOS and let it run ;-)
o and internal drives are fatser tha external
I have an 20GB 4200rmp drive inside my TiBook, and an external 80GB 7200rpm FireWire by LaCie, the internal drive is faster... I just was considering building an 60GB 7200rmp notebook drive in there for faster performance...