Most routers have a default configuration, that is not at all secure. Since this is a business, you need to sit down with the router documentation and decide how you want the lan to operate. There is a preset password, you need to change that after installation. If it is wireless, or you ever want to use wireless, you will need WAP encryption. If it is hard wired, and the wireing is secure, ( no public access ), then you usually don't need WAP.
DHCP or static IP addresses. If you want file sharing, then static IP makes life easier. DHCP if there is no sharing, ( you can get it to work with DHCP ) but it is more troublesome with DHCP.
Run the cables from each work station to the router, and plug them in. That is about it for the hardware part.
As stated above by another poster, the tools are different for configuring windoze and linux. If you want one person for configuring the linux systems, look into installing Webmin. It is available for all distros. It allows you to configure any machine through a web browser. All you need is IP access to the system.
If you have other questions, please ask, be as specific as possible.