Hi there.

normally SUDO is sufficient but (for beginners here - old users will probably know the trick so excuse- we were all noobs once !!) if you need SU access in ubuntu simply type SUDO SU and then you are in !!

Note though ubuntu rel 17.x has a little nasty in it -- running dolphin (KDE file manager) or some other file managers as root is not possible any more -- I thnk they've hosed this up - sometimes you need read / write access to root folders e.g samba conf etc. Still works in Ubuntu 16.x though.

I prefer for Linux GUI KDE to GNOME / UNITY but that's your choice of course.

Ubuntu 16.x probably a better choice as it is LTS (till 2021) whereas 17.x will be updated again in july but fine for testing as VM's.

For Gnome desktop on 17.x Nautilus can be invoked or run as root but you've still got problems editing / saving and a GUI editor is better than the hideous VI !!!!!!.