There should be a ground and hot wire for the fan already in the ceiling. If there is only the light fixture there should still be enough to run the fan as the fan does not use that much.
BTw - have you looked at the Maxx fan deluxe in lieu of the Fantastic Fan? I just installed one back in May and with the built-in rain guard. You can leave it open 24/7.
Steve, Christy, Anna and Scout (Border Collie)
1994 30'11" Excella - rear twin
2009 Dodge 2500, 6 Speed Auto, CTD, Quad Cab, Short Bed
Hensley with adjustable stinger
WBCCI # 3072
AIR # 6035