Actually, using Linux as a fileserver is pretty easy. (OK, I'm not a newbie anymore but still .. ;.) )
You need to think about how you want to set this up:
1) A backupprogram on your Windows-boxes that stores the backups on the Linux-server?
2) A server-side backupprogram - that is, a backupprogram running on the Linuxserver that backs up all users data?
3) Just create a samba-share on server that all users can connect to and do their own backups?
Samba is not that difficult to understand, it comes with a default config that is quite readable actually
The standard samba docs (http://samba.org/samba/docs/
for instance) should be sufficient, together with you reading the file /etc/samba/smb.conf (actually, if you're the least familiar with reading text config-files you don't really need the docs just to create a simple share.)
Now to my questions:
1) Depends on the program, what does it need? smb, ftp or what? As you are new to Linux take one thing at a time, just check exactly what's needed and learn about that.
2) You need to check the program - don't know much about these but there are a lot! You could use something like Bacula, but beware that one is competent AND complicated! There are several easier-to-use apps for your purpose, hopefully someone else can give you better tips on what program to try.
3) Very easy as I've mentioned earlier.
Once you have the share you can access it on the Windows-boxes just as you would a Windows-share.
... OK I realize I didn't answer your question - "Can anyone recommend a book or website.." but well, you got a few hints anyway.
And really, unless you want to go deep in seg samba, all you need is google - and take one thing at a time, don't try to find solutions to all problems at once!
(PS What do you mean with "what comes before 101?"?