Sorry, I've changed Macs and lost my app that makes scripts look pretty, but copy and paste should work!
--Put what you want to search for as the first parameter,
--and what you want to replace it with as the second.
--you can add as many of these as you like!
SAndR(return, "")
on SAndR(searchstring, replacestring)
tell document 1 of application "QuarkXPress"
-- the try...end try bit means it won't error if it doesn't find any instances of a given searchstring
try
set (every text of every story where it is searchstring) to replacestring
end try
end tell
end SAndR