You'll likely also want a power supply - the power supply in the G5 is right in the bottom of the case, and if the coolant has leaked onto the motherboard, you can bet its also destroyed the power supply. If you have to replace that many parts, its not really worth it IMHO...you'd be much better off stripping it, that motherboard alone is US$200, which is way more than you want to pay to repair a dead computer thats no longer supported by a current version of the Mac OS.