Ok I somehow managed to use file sharing to mount my g5 hd to the imac. Not sure what I did to make it work but it does. That is ok right?
You enabled G5 System Preferences -> Sharing -> File Sharing. Then on your iMac you most likely clicked on the G5 that appeared in the side bar of a Finder folder window. Or you use Finder -> Go -> Connect to Server, and then "Browsed" to find your G5.
You more or less do the reverse to allow the G5 to mount the iMac volume, although the G5 may need to use the Finder -> Go -> Connect to Server to make the connection.
I have another question though. My G5 is wired to the router the imac is wireless. What security settings should be made just so I can access my hd from the g5 to the imac. I am really clueless on setting security and all the how to articles I have read have probably led me to change one here and one there. Could someone please tell me what permissions should be set and what sharing info should be checked off and so on.
Since your iMac is WiFi, you should be using a form of WPA WiFi encryption between your home WiFi router and your iMac (unless you live in a rural area and it is unlikely someone would park withing 300 feet of your home to borrow WiFi services).
Since you are behind a home router, you do NOT need the Mac OS X firewall, as your home router is acting as your hardware firewall. This makes things very simple for you.
It is always a good idea to have a reasonably difficult to guess password for your user accounts on each Mac, but something you can remember.
And that is about it for secruity.
If we were talking about a laptop that travels to public WiFi access points, hotels, airports, and such, then there would be different rules for secruity you should use.
At this time I only need to have the new imac connect to the internet and be able to access files on the G5.
Since you have home router, both systems may equally access the internet (assuming any authentication your ISP may require (PPPoE maybe) is handled by the home router, which is what I do; if your ISP does not have any separate authentication, then you are all set).