The G5 is SATA, yes, and no ATA-SATA adapters wont work. Apple has a kbase doc on this.
If you want to keep your ATA drives, either 1. pick up some FW cases on eBay or a Sonnet ATA controller card.
Your 733 uses PC133 SDRAM, the new Dual G5 uses PC3200 DDR400 SDRAM.