Hoping somebody can help out on this..

Basically Im trying to set-up my office G5 Power mac running OS X 10.5 client version to allow it to be accessed across the internet securely such that I can read and write to it from my macbook whilst out and about. I appreciate that the office machine must be left on.. not a problem.

I don't have a server just 2x G5 Power macs on an ethernet network. The internet comes in on a Speedtouch modem and that is connected via ethernet to a Netgear wireless router/hub from which the ethernet is connected to the G5.

If anybody could point me in the right direction of what I need to do on the G5 and the routers that would be much much appreciated. Google throws various things up but not sure what would work and what wouldn't so a proven method would be good.

Huge thanks in advance!!!

you can do either screen sharing/SSH or something like FTP.

Either way you'll need to forward the appropriate ports on your router to your PowerMac which means than anybody can try to access those services from outside your network.

An alternative is to use something like Hamachi

It's a VPN client which should magically work over most firewalls, network configs etc.
It will make your two macs think they are on the same local network, and thus no firewall/router changes will be required.

All you do is make sure the file sharing/screen sharing service(s) you want are running on the PowerMac, then make sure Hamachi is running on both machines and it should magically connect them via the wonders of the intrarnets