I have a node that I'm trying to display differently based on what's in the argument.

If there is no argument, I'd like to display it normally. If the argument is "advanced", then I want to display the node using a template I create. How can I set this up...

Or more specifically, how do I know what template files drupal looks for when specifying templates? Do I set this? Where?

Also, can I pull in variables from this template file to pick and choose node fields as I wish?