Accessing text of a field with type "Text"
start by downloading the devel module.

A suite of modules containing fun for module developers and themers
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Devel
Helper functions for Drupal developers and inquisitive admins.
This module can print a summary of all database queries for each page
request at the bottom of each page. The summary includes how many
times each query was executed on a page (shouldn't run same query
multiple times), and how long each query took (short is good - use
cache for complex queries). Also a dprint_r($array) function is
provided, which pretty prints arrays. Useful during development.
Similarly, a ddebug_backtrace() is offerred. much more.

This includes a function dpm() which allows you to navigate through complex variables including $vars. dpm($vars) will create a user interface for navigating through it - then you can find the specific location for the field you want.
I included this as an answer instead of the presumed actual location of the field within $vars since this allows you future access to any variables you need. You can use this for example to go through a $form, $content, etc.