The warranty will not cover you tampering with it. It's an odd warranty though, are you sure you aren't mis-conveying it or misunderstanding? Because from what I gather, you are saying your warranty only covers the screen?
Hi newcomer and welcome to the Tom's hardware forum.
Even, if you kill your screen, when the manufacturer check the laptop they can find the other killed part, and the warranty only will cover the screen. So, you won't win anything with kill your screen, because you must pay to fix/replace the other part.