what can i do to my 2008 mazda 6 to make it perform better?

[Andrew]

it is a 4 cylinder and i dont know much about car modifications but i am trying to learn, so i was wondering what i can do to my 2008 mazda 6 to make it accelerate quicker and make it shift gears a little smoother and quicker, also if i were to put a mazda 6 v6 engine in it, would it work or would i have to change other parts as well