Can someone stop the cause of death after someone writes the details in the Death Note? Let's say I had a Death Note. If I wrote someone's name in the book and then wrote details of the death, can an individual stop the cause of death and the actual death entirely or will the death still take action, but in a different way?
The Rules of the Death Note are pretty clear:


  How to Use: XI
  
  […]
  
  As you see above, the time and conditions of death can be changed, but once the victim’s name has been written, the individual’s death can never be avoided.


This is, of course, as long as you thought of the victim’s face while writing the name. In case you now assume that you can just alter the details of death to something impossible, well sorry:


  How to Use: LV
  
  […]
  
  In the occasion where the cause of death is possible but the situation is not, only the cause of death will take effect for that victim. If both the cause and the situation are impossible, that victim will die of heart attack. [emphasis mine].


So again, all you get is a heart attack. The victim will die.

Tl;dr: Think before you write.