If your interface is up, then you are in the LAN. But the issue is sharing resources you want.
In Linux you usually don't get 'My Network Places' like thing to interact with Windows boxes. If you want to share resources within the LAN you have to implement specific service like Samba, NFS, SFS, FTP, etc.
If you wish to share files and printers seemlesly you better opt for Samba. I cant teach you Samba with one forum posting. It's good if you try to read tutorials and other documents in the Net. And stay in touch with LQ. LQ is here to help.
Samba.org will point you to a lot of docs including their official Samba docs. Samba howto collection is also there.
Google Linux Search shall lead you to a wealth of information.
By the way, as I usually do to other people, I'll advice you to switch to a newer distro. Red Hat 7.3 is really old. This may give you head aches. If you are familiar with RPM stuff and want to remain using Red Hat related systems, try using
Fedora,
CentOS, Tao, WhiteBox, etc.
