If you don't have a legal copy of Windows 2003 R2 SP2, you can register and download through Microsoft's 180 day trial option. You can find this on Microsoft's website here.
File sharing should always be set up on a different physical drive on the server, or at least on a different partition. If you fill the partition then its not as critical as if you fill your system partition.
My preference is to set up a Data folder with subfolders corresponding to drive mappings, rather than sharing the root of the drive.
Conventions for printer sharing
Conventions for AD/OU setup
My rule of thumb is to always set up an OU for the company at the root level named for the company.
Within this, structure OU's for Users and Computers.
In general, Computers will then be populated with two OU's at a minimum: Workstations; Laptops.
Users generally will not be populated with any other OU's.
Generally I don't set up any sites and change the default Site configuration with a single server. If you have multiple servers then you need to identify whether these servers are in distinct areas (and subnets) or not. If so, they should be set up in seperate sites. This lets computers automatically recognize that they should be talking to the local DC rather than falling back on the default behavior of round robining through all available DC's (and potientially timing out as a remote DC is unreachable or slow).