As a Computer Consultant my first point is....beware of advice you get from a big box store employee.
They are there for a reason....to fetch the product that you have researched and know you want.
I work on Windows and Mac networks. SOHO/Medium Offices/Schools.
VNC is remote desktop management/control not file sharing or Windows networking.
We do not work from the beach!
You know what sand does in your shorts! Now imagine that in your computer innards!
Poolside on a bluff overlooking Cape Cod Bay or Nantucket Sound...Possibly....
An Ashton and with nice Straight Kentucky Bourbon you bet!
Networking Windows with different OS can be/is a PIA.
My motto is KISS.
TCP/IP is your friend.
I like Linksys and use their products almost exclusively.
Other companies when they have an excellent niche product.
Overly complex systems only break down easier.
So...you want it to be easy....and almost fool proof....that even a member of the Democratic Party could not screw it up!
Notice, I did not say Democrat....
Use this...less than $150....it does what you need and then some!
This link is broken, either the page no longer exists or there is some other issue like a typo.
Every computer goes to it...so no networking worries.
You can make public and private folders for your network.
No other computer has to be on.
You can even get to it from outside of your house with FTP.
A good way to have a simple 'server' type product for non 'computer geek' people.
This is the best 'free advice' you can get for a simple, easy and inexpensive networking/file sharing device.
Now where is that coal shed?