Yes you can just use file sharing on the mini, nothing extra needed but a good DAS concept.
If you find you want to add a time machine destination, a web server, a email server, or have finer shared folder control on .... etc you need the server pack.
I found setting up web services, TM destinations, and file sharing to be strait forward and a no brainer. The server package help files and setup guides lead you through without complication. If you need different permissions for shared folder or disks, then thats easy to set up with a server package.
The server package has other thinks one could toy with, but you need to know what you are doing... and that learning curve can be steeper. Otherwise its a no brainer
BTW there seems to be less issues with Mavericks and Mavericks server software than Yositime.