funcation to use in select

Oracle 11gR2
I am new to PL/SQL function and need help. your help is appreicated.

I need to create a function that needs to be used with select statement, ie. select dquote_comma_convert(street_name), quote_comma_convert(patient_name), quote_comma_convert(2nd_address) from patient_info;

***** Requirement:

·           Pass into the function a string (varchar).

·           Test the string for double quote (“) and comma (,) characters.

   If string does not contain either of the test characters then return the string passed into the function

·        I  1. if the string contains a double quote (“) in the string then do the following: