gm9 has a seperate install for the market window found here:
http://www.eq2interface.com/download...ketWindow.html
So all you should need to do is first install ThorUI and once the install is complete download and extract the file above to your ThorUI directory. (Likely C:\Program Files\Sony\EverQuest II\UI\ThorUI ). Overwrite whatever it asks for and you should be good to go.
Hope this helps!