Download the zip file, euserrep.zip, unzip it and one dll file, 
euserrep.dll, will show.  Put that dll file in your plug-ins directory 
under your main, Eudora directory.  Close eudora if it is open and reopen 
it.  Start a new message or reply to any post.  Go to the edit menu, then, 
the message plug-ins item.  Arrow up or down and you should see the search 
and replace, plug-in.  Hit enter to see what it looks like. It does work like
the search and replace in MS word. you can search for a string and replace it
with something else. You even have the option  of having the search string 
being case sensitive.