If file and print are the most common use case for a workgroup server, then providing all the various network services you need for a small network comes in a close second. These typically include things like DNS, DHCP, Firewall, remote access through either SSH or some type of VPN. You probably don't want to put all of these services on the same machine especially if one of the roles will be firewall.
Configuring an openSUSE machine to act as a firewall will require a minimum set of hardware components, not the least of which will be two network interface cards (NICs). This lets your machine have one connection to the outside world and a second to the internal network. openSUSE 11.0 comes with SuSEfirewall2, a stateful network packet filter based on the standard iptables service. All of the configuration options are available through the YaST utility on the Firewall page.
DNS and DHCP are also configured from YaST as is the Samba Server configuration. DNS is one of those services that you'll need to get smart on especially if your network has more than a single subnet. In most instances you'll have named services within your internal network that you will want broadcast while at the same time linking to an external DNS provider for Internet name resolution.