How to tell Stringsoverrides module to replace text only in specific module?
String Override works for the strings defined inside t(), t() takes context as one of the parameters, for example

1. t('May', array(), array('context' =&gt; 'Long month name')
2. t('May', array(), array('context' =&gt; 'Abbreviated month name')


Both the strings are 'May', if you replace it would be changed across, but t() function also takes context, so if you provide the right context, only that instance of sting will be replaced. String overrides also takes the context while replacing the string, you have to make sure the string you want to replace in a moudle passes through t() and with what context.

Other way could be if its a variable then do a variable_set()

What I prefer is to patch the module, keep the patch in patches folder. To me string replacement is not mission critical peace, after next update release we re-do our patch.