hello 1sy8,
the superuser has no passwd, so becoming root should work without asking for password.
su - or sudo are both fine.
I have no xfce image here, and downloads are lengthy for me, sorry.
Intel gigabit cards don't need firmware, so you should be able to configure your network.
Either the graphical network-manager (or nmcli) or the ceni commandline tool should do the trick.
greetings
musca