please post if you have any
No, you can go look for them what do we look like slaves? The only mods your going to be finding is campaign and single player mods.
Here are some YouTube videos on how to mod Mw3. You can get the mods if you just follow the video. 
Hope this helps.
Edit - What Gengar said is right. All you are going to be able to mod is campaign and single player. Your not really going to have fun with these mods. And also the likely hood you get banned gets higher if you try to mod something else besides Campaign.
The 3rd one you can do it on your xbox now, No modding needed.