Ghost Recon Phantom Engine.....

So you mean creating a 3D game right?

Nop, i mean reversing Ghost recon Phantoms Engine Functions, that the game uses to do stuff like drawing text, check if the player is visible, getting bone position etc.

Would this involve changing the installed game files? If so, wouldn't the server detect the changes and the game would not even run in the first place?

what, no man, havent you heard about making engine hook? To make it simple, we reverse the game functions and check what they do and then we use those functions in our hacks to do stuff.