1- you dont need all the CDs/DVDs. D/ling all the CDs/DVDs is pretty much d/ling all the repos. Theres a few reasons why the full repos are aviable on CDs/DVDs, I've found it handy for people who live without the internet or have very, very slow internet.
You can just d/l CD1 (or Xfce CD1/KDE CD1/LXDE CD1) and install from there, you will get a running desktop.
2- the CDs have (most) network card drivers on them. Debian (and other linux distros for that matter) will not be using the windows software/drviers.
3- too many answers, not enough information.
Last edited by cascade9; 02-19-2014 at 04:10 AM.