What is Lady Macbeth's plan to kill the king? Are there any flaws in her plan?

Her plan involves getting Duncan's guards drunk as well as putting some sedative in their wine. She wants Macbeth to kill Duncan and then smear the king's blood on them. Macbeth is to leave the daggers with the sleeping guards to make Duncan's murder seem their guilt. There are many flaws with her plan. Macbeth really is not cut out for murdering people, especially the king. The guards would have no reason to kill the king unless someone paid them. Why would the guards kill the king and then pass out in front of his chambers? Granted all of these obvious questions are not asked but I think they are implied.