Caution - if you want to make models for the ORIGINAL CFS (ie. CFS1), then no, gmax will not help you. You can only use gmax to make models for CFS2, FS2002/FS2004, CFS3.
AD2000 (Aircraft Designer 2000) COULD make FS98 type models (which is what you would use for CFS1), but that is also out of print. I do not believe that AD2002LT (the free "light" version of AD2002, available on this site) has the modules necessary to make the "old" models.
BTW - the gmax support and download pages are better at turbosuid -
http://www.turbosquid.com/gmax