Windows uses dhcp, so the easiest way would be to set your linux box up for dhcp as well. It's easy, normally a single command that sets things up automatically, but without knowing what distribution you're using, I can't give you the exact command. Chances are, if your box was hooked up to the network when you started, your network was already configured...which may mean undoing some of your changes.
As for routing the IP so other boxes can see yours, that's probably not the issue. What you need to do is set up Samba (Linux's way of talking to windows boxes...because MS is scared to death of making their OS compatible with Linux). At first, just to get it going, set it up as a client, then, when you know more about how Linux/Samba works, configure the server.
Most "mainstream" distros (Redhat, Mandrake, SuSE) have easy to use configuration menus for doing this. Personally, I think it's easier to set up networking/sharing with a Linux box to a windows server (or vice versa), than it is to connect a windows box to a windows server. If nothing else, all the options are in one or two windows/menus, not spread all over like in windows.
It's awkwards moving to Linux, and a lot of things seem like they should be harder than they really are. Many of us have moments when we look back and kick ourselves because we thought something was "so hard", and now realize that we were just looking at the problem wrong. If it helps, once you've gotten so used to Linux, you shake your head at how pointlessly hard MS makes it to use windows. So, be prepared for a little "unlearning" of bad habits.
