For the ATI drivers, as lagagnon mentioned, you needed to follow the instructions on the ATI website.
As for the package management, I guess you needed to enable the "extra" repository.
The WM being "annoying" is something that can be easily changed. Not only you can play around with the XFCE settings, but you can install other window managers through slapt-get (e.g., fluxbox, jwm, kde, gnome)
As for DHCP not working automatically, I don't know how to solve it, but (so far as I know) that's not a problem that is very common.
Of course, if it didn't work out for you as a whole, not much that can be done...