Awesome, the whole story. Starting from the fact that you faced an average workshop who does not know their own stuff but you did not give up. Unfortunate that your dad cannot drive the car without the additional equipment but he is lucky having a son like you.
My first thoughts about the pics were that the metal joints do not exactly match the W222 interior but do not look too bad for the purpose. Could perhaps be made even better with some covers if possible but reading further I noticed you had already looked at that.
I'm sure you will both enjoy the new car.