Also it is much easier getting the fan correctly aligned on the stand of rubbery bit if you have the screw removed.

There is a grove in the casing that might be difficult to align. If so use gravity to allow the power unit to fall into "place".

I used two 2.5 mm drill bits, turned upside down. They worked like a dream. It took me a little while to realize that they needed to be lifted slightly from the underlying case in order for the board to slide out.