I'll try to clarify a litlle a bit bro...
There are in this moment 3 major mods bro, Grey Wolves, NYGM, IUB...
You've got to chose from one of those...
Example:
You chose Grey Wolves (GW)
Download topic
http://www.subsim.com/phpBB/viewtopic.php?t=50034
After you enable the mod You have to download the recent patch update from GW...
Here
http://www.subsim.com/phpBB/viewtopic.php?t=51468
Then lets say you whant the merged campaign from NYGM, you download the Unified Campaigne GW
Here
http://www.subsim.com/phpBB/viewtopic.php?t=50377
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This was the main 3 mods for operating the GW version with the
NYGM Campaigne included, the rest is a question of adding optional mods that are usually marked with the name off the modd they are for...but that will be your choice...mate
hope this helps somehow bro...