Follow 247's advice with the lights, then get something like this:
AGA Versa Top Full Glass Aquarium Canopy 72 x 18"
http://store.seacorals.net/agaaqglcawip.html
Does your tank have 1 or 2 braces on top? The AGA top is for 2 braces, you'll need a Perfecto/Marineland one if your tank has one brace. I just today bought a glass top for my 125, so have done the research. It was much more expensive to try and have a glass top cut at a glass shop than to just buy it. Lowe's, Home Depot, etc. could not get or cut glass thick enough to use. My LFS got me one for AGA for $46.00.
Good luck with your tank. I, too am setting up my 125!! Mine is high liht for plants and I found an amazing fixtture for $200ish, but would be way too much if you are not doing plants, and your Oscar, etc. would make plants impossible