How to modify the layout or look-and-feel of a specific node?
One of the things you can do to help with this is to enable Theme Debug mode, see here:

https://www.drupal.org/node/223440#theme-debug

This will tell you what templates are currently being used, and will provide suggestions for what templates to use, when you inspect the source of your node page (the suggestions are in HTML comments, so make sure they're enabled in your inspector).

It also details how to create your own custom template suggestions, the patterns of which is detailed here:

https://www.drupal.org/node/1089656

Make sure you place the templates inside your theme directory in order for the theme to pick them up.