You don't need tutorials to do that, you can draw the weapons by yourself in paint, and then you can replace them in the folder where the original images are, but you can never change they're names. In you're soldat folder there are the sub-folders where the weapons are:
- Weapons-gfx,here you have the weapons as they appear in your guy hands;
- Interface-gfx, folder that has the images of the interface, like the ammo, health, etc;
- Interface-gfx\guns, the weapons as they appear in the weapons menu;
- Sparks-gfx, this folder contains content like blood, flames, explosions, etc;
- Sfx, ingame sounds;
- Textures\Objects, these are the game elements like health packs, grenades, flamerkit, etc.
That's all.