Help my 2nd compy find the Net...

Hello there. I managed to connect to the Internet without wasting electricity on a Windows machine to do the dirty work.. Anyways, now I have to basically turn my Kubuntu Linux machine into a "gateway", or rather a router...

I googled up an article, and it seems to -almost- work, but has a lot of noticeable shortfalls when I tried it. Link is here - http://www.cyberciti.biz/tips/linux-as-router-for-ppp-pstnisdn-connections.html

There seem to be a couple problems I notice right away:

• The other (client) machines on my network can ping the router machine, but still can't get past the local network..
  
• IP forwarding sounds rather dangerous/insecure, and I probably only want to do it on my ethernet!
  
• Also, does the gateway machine have to have a specific IP address like in Windows? (192.168.0.1, I remember it like friggin' PI )... I hear in the UNIX world, it doesn't, but that was just hearsay :P
  

This article looks like it could be totally wrong, and thankfully I was able to easily reverse the whole operation :P So please help me get my internet properly routed without using a "Windows Gateway machine", thanks :D

EDIT: I eventually got it. I ran sudo ifconfig eth0 inet 192.168.0.1 up, but it seems I have to to the "sudo iptables" on the gateway machine in order for the client machine to see the gateway.. I have a feeling modifying sysctl.conf makes my system less secure though :P