Samba is designed for you to access resources between them, but has nothing to do with Internet connection sharing. You should search for mandrake's network setup. If you have two ethernet cards, Mandrake knows that. If you find the correct setup, there must be some place where you can enable connection sharing. It shouldn't be difficult, I did it myself, times ago with Mdk 8.2.
Under redhat 8.0 it was "Kernel tuning". In my current suse, it's Firewall option. It changes from distro to distro.