Insanity Workout - Tips & Where to buy?

Hi! So I have been doing my research and I have decided to give Insanity a try. The only thing for me is the $140.00 price tag is pretty steep for a college student.. Is there anyway to get it cheaper, or anyone know of any stores that may have it at a discount? Or, are there any comparable workouts that I could get for cheaper? I am willing to pay a bit of money for it - just not THAT much.

Also, assuming I do buy it, any tips? I'm pretty prepared to get my butt kicked, but I'm worried about what to eat while I do it. I know that I'll have to eat more because I'll be doing a more intense workout, but I'm afraid of over-eating too. And I'm smaller (5'0" and about 115lbs) so I will burn less calories probably, right? Right now I ear about 1200-1300 calories with no exercise, and more if I'm doing an intense exercise but normally I kind of just guess.

Any help would be great, thanks!!