You can find walkthroughs by googling a bit (I myself wrote walkthroughs for the last 4 levels), but I'd highly recommend doing it without cheating. The amount you learn from figuring it out yourself is exponentially more than what you learn from reading a walkthrough. Most important is how you learn to think, by carefully looking for vulnerabilities and examining what you have control over and how the program uses your input.

Spend enough time learning the instruction set and the concepts involved and the answers will become apparent.