Hi Sandeep,
Thank you so much for your suggestions. I like the idea of hardwiring our stations. The ones that are, are so much faster.
What is a gigabit switch?
We don't use sharepoint or exchange. I would like to utilize them. I want to start with fresh software for the server-will have to use the AC data we already have.
I am so afraid of this process. Thanks for your help.
Don't be afraid, you have the great power of the ACUB behind you

A gigabit switch refers to the speed of the switch. Traditional switches typically have transfer speeds of 100 Megabits or 12.5 Megabytes/Second. Gigabit Switches on the other hand have 10 times the speed which is 1000 Megabits/second (1 Gigabit/second) or 125 Megabytes/second. Let's assume you have a 20 Megabyte video file which you are trying to transfer over the network. That'll take about 2-3 seconds to load off the server on a 100 megabit switch (assuming you are around max speed, which isn't realistic). On a gigabit switch, that would take under 1 second (even at half speed). You said you have 15 computers. With everyone loading and importing items into AC and other folders on the server, you can saturate the network pretty quickly on a 100 megabit switch. A gigabit switch on the other hand would give you 10 times the wiggle room. It really doesn't make sense to not go with gigabit as it's only slightly more than a traditional 100 megabit switch.
For 15 computers, you're probably going to want to get around a 24 port switch. (There's a 16 port version, but that means all the ports would be used. Not much expansion available with that.) There's also a bunch different types of switch Unmanaged, "Smart", and Managed. A fully managed switch isn't really necessary for a small office. An unmanaged or smart switch should be sufficient. (Unmanaged is essentially plug and play. No configuration necessary). Instead of having you do a bunch of research, here are some good switches in my opinion: (I'd probably get the third one since you can enable the managed features if you need them in the future, if not, just plug and play).
Gigabit Unmanaged Switch Good:
D-Link DGS-1024D Rackmountable Swit...B Buffer Memory per Device Buffer MemoryGigabit Unmanaged Switch Premium:
Cisco Small Business SR2024CT-NA Un...10/100/1000Mbps ports, 2 Combo SFP portsGigabit Smart Switch Premium:
Cisco Small Business SLM2024T-NA Gi...+ 2 x RJ-45 Uplink + 2 x Combo mini-GBICWiFi is a completely different story. Transfer rates are rarely as high as they advertise. You also get dropped connections as well as higher latency which just leads to a slower experience.