@markusgeiger if you are looking at the K3LK4K40BM-BGCN remember that this memory IC is a 496 FBGA (lots of tiny little solder balls in a very limited space ;-) . That is one of those tasks that I would suggest you have somebody doing it that has done it before.
That is not to say that you can't do it yourself but practice on some older boards first. Don't do this ion you S20 if you have not done it before but practice first. [https://www.youtube.com/watch?v=0zq98wqEZlo|this video] is pretty good about explaining some of the techniques to do this kind of task.
In short, my tip on this is to practice a lot. YouTube videos are great for the How-to but are no substitute for actually doing it. There are big differnce between watching somebody that has done a lot of these IC doing it and doing it yourself.
It'll be a lot easier with a BGA IR rework station :-)