I'm new to Windows 2008 but would like to know whether it still has the same
functionality of earlier versions.

I assume that if I were to install two servers (2008 Standard) I could still
make one a PDC and the ofther a PDC such that people would still be able to
log in to the network if the PDC were 'offline'

Is this also true of SBS.....if I were to have Small Business Server (2008
Standard) on the first server and Standard 2008 on the second?