Wow. Welcome to MPGH James! You really look like you can contribute a lot to this site.
There are 3 type of modding (as I know of).
- Texture modding
- Cross-modding
- Hex Editing
Texture modding is just changing a skin of a gun. You can create your own with Photoshop or Paint.Net. You can creates textures of anything in the game!
Cross-modding is changing one gun to another. This has a few benefits depending on what gun you change your weapon into. These can include: Faster rate of fire, faster reload time, and faster deployment time.
Hex Editing is editing the codes in the weapon files. With Hex editing, you can change the RoF without cross-modding or make a no reload mod for a gun. For now, that's all I know with hex editing.
Good luck and have fun at MPGH!