Hi i I bought a 2001 z24 in august and i'm already having some problems with it. First my passenger side window no longer works and its stuck at half way down position. I'd assume this is the motor for the power windows? For a while it would let you put it up a little or down a little at a time but now it doesn't work at all. Secondly whenever I got to stop rapidly I get a knocking noise and the car lurches forward on occasions. I also hear the same knocking noise when I make some of my turns. What could be causing this and how expensive will it be to fix?