Games - Marffy

My old game has been deleted because of a computer failure. Now I am currently looking into the unity engine for a better and funner version of my game. If you know a thing or two about unity you can always help me bye giving some info, or leading me to a tutorial, right now i am learning the basics such as importing models, making weapons , making maps, etc... Also, i am trying to make a mod for l4d. Its going to be a realism mod, anybody who has the knowledge of putting iron sights in the game can pm me please.