Welcome to TS, zeyeman!
I can assure you that adding a second drive to a G5 is like a piece of cake compared to adding one to a 9500!!! Not only is access extremely easy, but it's basically plug 'er in and off you go.
You can find Apple's instructions here:
http://www.apple.com/support/powermac/doit...lf/storage.htmlWhy they say skill level is "intermediate" is beyond me - if you can use a screwdriver, you can do this...All you have to do is attach the drive screws from the drive bay - Apple provides them and you'll find them on the side of the drive bay - disregard their bit about discarding them - clearly they think you'll be ordering the drive from them - slide the drive in, attach the two cables and off you go. Drive jumper should be set to "cable select" - usually there is a diagram on the drive to follow. Reboot machine, use Disk Utility to do whatever formatting and partitioning you want to do. Beyond that it's up to you - you could clone the current drive, install a fresh OS, or just use it for storage.
Obviously, you do NOT want to order this item from Apple!!! (Price likely to be ridiculous) Plenty of great sales out there - if you haven't bought the drive already, you'll need a Serial ATA 3.5" drive. My personal favorite is Seagate because of the 5 year warranties; I have about 4 of them in various Macs at the moment. NewEgg is a good (inexpensive) source for drives, but you can also check the lists at
http://dealmac.com .