Best way to modify language strings is not to change the default files.
You should download the english language plugin for CB 1.3 from here:
forge.joomlapolis.com/projects/lan-cb-en/files
unzip it locally.
Then modify any string you want from the individual php files.
Example:
english.php file has strings like:
[code:1]DEFINE('_UE_HITS','Hits');
[/code:1]
you can change this to:
[code:1]DEFINE('_UE_HITS','Views');
[/code:1]
cbteamplugins_language.php file has strings like:
[code:1]'Profile Book' => 'Profile Book',
[/code:1]
you can change this to:
[code:1]'Profile Book' => 'Guest Book',
[/code:1]
(notice only the second part is changed above - if you change the first part the the default language files will kick in - you should not change the first parts here!)
there is also the admin_language.php file that contains strings used in the CB backend. For example:
[code:1]'Provides an User Tab that shows all articles written by the user.' => 'Provides an User Tab that shows all articles written by the user.',
[/code:1]
can be changed to:
[code:1]'Provides an User Tab that shows all articles written by the user.' => 'Gives User Tab that shows all articles written by the profile owner.',[/code:1]
Notice above that only the right part of the => should be modified.
Once you make as many changes as you want above, rezip the previously unzipped folder and install the resulting package using the CB Plugin Manager.
This way your english plugin will be used instead of the default language strings that CB has as a fall-back mechanism.
The above method should be used as your changes will not be over-written when upgrading to a newer CB version.
Hopefully things are clearer now.