Creating a content type that merges fields with its assigned area within the body
I think it sounds like you want to write a node template. http://api.drupal.org/api/drupal/modules%21node%21node.tpl.php/7

Basically you are going to create a template file called node--content-type-name.tpl.php and in that template you have access to the $node object which contains fields. Then write your html and use the values from $node.