Re: the last question;

Yeah, it's pretty easy. You can right click the drive and go to 'share this drive' or whatever, and you'll give it a name you can access it from across your network. You set whether you want other users to be able to alter your files (yes if you plan on doing it or don't care, no if it's strictly for you sharing to them). To access it, someone will need to be in your workgroup (for fast justice, but not strictly required), and to know the name of your computer, and which share it is.

If my workgroup is DEADMEN (which is is), and my computer's name is SALVATION (which it is), stu would have to be a member of DEADMEN (on windows, OSX just shows all workgroups, and I assume that *nix is the same. I don't have a clue how a windows user would find a share not in their workgroup frankly), navigate to network places in windows (or probably Network in *nix), click the icon that says SALVATION, and a dialog will pop up asking which folder he wants to access.

Basically the same as folder sharing for any other folder.

You don't want an external usb drive? xD