Fans vary with case, looks like the 300 comes with a 140mm top and a 120mm rear. Mounting spaces for more, I'd suggest at least one 120mm (120x120x25) for a front intake, and if you want a side intake, get another of the same for the side intake. I'd suggest sticking with TriCools if you put in any of the optional fans, they are excellent fans.
http://www.antec.com/us/productDetails.php?ProdID=15300
Cables come in the motherboard retail box, and a very nice set of box contents it is with the P5N-D.
http://www.newegg.com/Product/Produc...82E16813131232