Need some help with a file server!

Hi,
I'm wanting to get a mac mini or the mac mini server (whichever is needed) and connect all of my random external drives i have lying about to it. Basically, i'm wanting to set up a mini file server that i can access from anywhere in the world. I have enough space with the external drives to store my music library, other general storage and maintain a backup of my OS drive and portable external that i carry around with me, but i don't know how i'd set it up so that i could access my hard drives and use them normally from anywhere.
Also, with Mail Server, i'd like it if i could store all of my emails on the server computer and be able to access them on my Macbook. I don't know what i need though. For my needs, do i even need the server program or can i just use Lion (or even Snow Leopard if i choose) by itself? And if i did need the server, would i need it on just the server computer or both the server and my Macbook?

Sorry if i haven't explained this very well, if you didn't fully understand just ask me and i'll try to rephrase it.
Thanks in advance
mrmeister