You should hit up the aerodynamics section. I recently made a partial pan for my Honda. It's a relatively common modification and you shouldn't have any problem finding some information on the topic.
I probably won't be the first to say that you might be better served by getting a more efficient vehicle, if it can suit your needs. 120 miles per day comes out to $8000 in gas per year, which means the break-even point of something like a Civic or Corolla would be well under a year, even if you kept the SUV for hauling stuff.
EDIT: As for the hood scoop, that's likely to be counter-productive. Increasing intake air temperature can give benefits to mileage, while cooling it off may rob mileage but give a small amount of extra power. Taking weight out of your vehicle will help more in the city than on the highway, but your break-even point will be pretty far in the future because the gains are not large, especially if you're doing mostly highway driving.
EDIT2: Check out the stickies in the top of this section too, specifically
http://ecomodder.com/forum/showthrea...-mpg-5170.html