Welcome to Subsim
I would be a little cautious as I can't remember if Gameshadow has a copy of Greywolves & GWX
. Greywolves was the first offering from the Greywolves Team whereas GWX is the latest.
To verifiy which version you have installed on your system, when you load SH3 you will be presented with a 'howling wolf' intro if you have GWX installed. The version number will appear on the next loading screen.
Instructions for installing & preparing for GWX & Patches can be found in the manual, which you can view online by clicking on my sig. Also, be advised that all needed files and information is contained on the same site.
I hope this helps.