Finally the audio jack was replaced with the line-in jack. The picture below shows the result. As you may notice there is only one jack left.
Btw, thanks to Mario “The master of circuits” W.
So the reassembling process could be started. I was very suprised that the whole process took only 45 minutes and that the damn thing worked afterwords. The next picture should supply evidence:
But as in every reassembling process there was one part left. A damn little screw :-)