The guide is 100% ok, just it seem that there was some "issue" with the IO board, since I am abroad it was easier for me to find another solution locally since I needed to solve the issue and was not able to wait for the whole process of claim a warranty on the board.
I had the same "no audio" (mic) issue with an IO board (purchased from ifixit also, p/n 5000826, IF 188-069-1), I took my MB to apple service and they installed an original IO board and got audio back.
Lorsqu'il en aura reçu, il pourra afficher un graphique de sa réputation au fil du temps.
Voici un aperçu de ce à quoi ressemble ce graphique :
Aucun point de réputation obtenu pour l'instant.