Yes you should as airflow is important in a pc. If there isnt enough all the the hot air gets trapped inside so you should get fans. The amount of fans needed is your choice, the more the better thus if you arent going to overclock you dont need to get an after market cooler.
Yes, like it has been said more fans the better, but only to a point. I have 4 intake fans and 3 exhaust fans (two of the exhaust fans being set up to a radiator). With that case, having the fan in the front, bottom, rear, and top x2 would be plenty, and if you wanted to extra umph, go pick up a simple liquid cooling set, such as the Corsair H100i (if you want the 240mm radiator - mounted on top) or the H80i (for the 120mm radiator - mounted to the back).