Applescript needed to check Quark doc for characters and replace if found.

Hello - I need an applescript that can look at all the text boxes of a Quark 5 document and replace any of a list of characters that it finds with another value. A PC server renders web based orders into text that we use Xdata for and in the process, any foreign language accents get turned into another encoding. What I am thinking is that for example "%" always shows up for "ü" so I want the script to look for "%" and if found replace it with "ü" - There is a list of about 18 so far that we are finding but I am sure with a script of two or three, I can edit as needed.