You can go download the trainer for the game if you want. I believe it is ThirdEchelonUser.ini You might be able to download it from the "Evox Trainer Depository" or something like that. just search in a search engine.
All you have to do is swap it out with the existing .ini file. If you want to change the controls ect - like which buttons to hit to make you invisible- open up the .ini file in a text editor and swap out the values for the controlers.
The .ini file clearly labels invisible, invincible, ammo ect. However to change the speed you have to go hunting a little bit inside the .ini file - i forget where it is, but i did mine so he runs a lot faster, and when he is crouching he can go as fast as running, and still be quiet. If you want to change the speed and its not in ThirdEchelonUser.ini, then there should be another .ini file inside the SAME EXACT directory. I forget which file but it is definitely a .ini
Hope it helps.