No offense, but you should hire someone. It's gonna save you headaches now, and especially when it needs expansion/upgrades/repairs down the road.
Someone with some experience in this area is also going to ensure that things like DHCP are set up correctly to leave a hole for static addressed devices like printers & scanners, DNS so you can find network devices by name, ensure you have a proper backup system in place with a regular offsite rotation and retention policy, make sure you have some sane ACL's set up on file shares, ensure your router is properly secured, automated patching strategy for unattended updates to the server, etc.
Properly done, its going to be a one time expense that will continue to run without issues, and allow you to concentrate on your real work.
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-Scott
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