Quote Originally Posted by scruffyeagle

I understand the su command invokes the superuser identity, but what does sudo do?
sudo is "super user do". It lets you exectue commands AS root without actually becoming root. Of course your username must be in /etc/sudoers for this to work.

...and, how does one close the console to return to X, after finishing the su tasks that made the console necessary? I've been afraid to use the console from the HD installation, because I don't know that. From CD boot, there was no problem - all settings would be reinitialized during the next boot.
Methinks we're talking about 2 different things. A console (a.k.a. shell or terminal) is just another window that runs inside of X.

You can switch tty's however (virtual terminals) w/ the CTRL+ALT+F? keys. Example:
CTRL+ALT+F1 gives you a virtual terminal and CTRL+ALT+F7 brings you back to X.

But, from HD, I suspect an improper shutdown could really screw things up.
Well it's certainly advisable to shut down properly but it's not a big concern (at least not like wimpdows). Linux journalized filesystems don't drop file fragments al over the hdd when it gets shut down improperly.