su is a command in UNIX which lets you temporarily jump into "superuser" mode to do administration tasks.

sudo is a prefix which you can add to any other command to say "do this command as the superuser".

What screen rez do you use normally?

Do you know what graphics chipset you have?

XOrg is the X Windows system.

Their website is here.

There will almost certainly be a hardware compatibility list and some troubleshooting info.