Welcome to AA JBFett!
Well first off...venting, should be as much as possible. Those lights are not going to put off much heat. When you get to using MH
lamps you will generate some heat.
I am almost finished with my top for the same size tank as you have. If you are pressed for money and need to put fans into your top, you can always scavange a couple of fans from a computer power supply and use them. The fans I used on my top are about 25 dollars a piece without the grills and cords, but you could improvise on them if needed. Here is the link to my top.
125 Gal-35 Gal Wet/Dry-Tetra-Tec PF500 HOB
(3) AuquaClear 301 Powerheads-600 GPH
Automatic Tempature Controller
5-6 Inch Sand Bed-200+ lbs of LR