Modeling is a huge art in itself - you won't be able to learn it in an afternoon. As for tutorials, it varies with what program you're using. Each has its ups and downs softimage is easier to use than 3DS, but 3DS has more support - and thus more tutorials. Other popular programs are blender, zbrush, and Maya. Note that many of these cost money, and can get VERY pricey - in the several thousand dollar range. There's a great tutorial on the process of building a hat on the steam user forums, it's a sticky on the tf2 board so you can't miss it.