Software used : Photoshop with its VTFEdit Plugin.
-The folder "materials" goes to "Steam/Steamapps/YourSteamAccount/insurgency/insurgency/".
-Replace everything if asked.
-If you want only the SVD crosshair, delete the "crosshair_l42a1.vtf" in the folder "lense", and vice versa.
-If you want to modify and upload these skins you can do it without asking my permission.
-Thanks to Logan Dougall and Fibbs from Gamebanana who helped me.