Belly fat question.....?

ugh, okay.. I lost 20 pounds by walking on the treadmill everyday, and doing a few sit ups or whatever. I still have a belly, probably because i didnt do enough sit ups. its smaller though. My friend said if its misplaced fat i might need to get lipo, and I will never be able to afford that. And that mabe I will need to do crunches for half hour a day. half hour of crunches. x_x i dont think i'd be able to handle that. My back muscles are extremely weak from bad posture, I'm trying to fix it... What is a crunch even? I dont even know. <_> Anybody have any advice on what I should do or whatever? :\