Here is a link to the IP-Masquerade-Howto. It gives very good details on how to do what you
are trying to do.
http://www.ibiblio.org/pub/Linux/doc...ade-HOWTO.html
The first thing you need to make sure is that you can ping between both machines. Once you can do that, setting up the IP-Masquerading is pretty straight forward. (It has been a while since I have read the HowTO, but if I remember right it doesn't go into much detail about setting up the ethernet cards (that might have changed). This should help with that.
http://www.ibiblio.org/mdw/HOWTO/Ethernet-HOWTO.html
Hope I have been helpful. I'm not trying to tell you to RTFM, but these howto's were written by people far better that I at setting up this stuff.
Cheers,
Forrest