Product review (3 stars): buying two sections of duct (or one if you feel like crimping the ends) an elbow
Certainly not worth the cost. Had to modify the knockout plug as it was made for a round hole and my model has a flat side to it.

While this part covers a lot of different makes and models the generic instructions say to remove the front of the unit. They also say that the lower front panel must be removed then remove belt. My model, Whirlpool WED86HEBW0, has no lower front panel and after removal there is no way to remove the belt. I ended up removing the back also to get the belt off. I also found a video from an online parts seller that was the same outdated instructions.

If I had to do it again I would remove the back, remove belt, flip on its front and try to remove duct from blower housing. There is only one sheet metal screw holding it and I think it could be reached. Also instructions say the control board needs to be removed. On my model it would only need to unplug some of the cables.

In all going to a hardware store, buying two sections of duct (or one if you feel like crimping the ends) an elbow, a piece of sheet metal to cover the knockout hole, and a couple of clamps, (or foil tape) a few self tap sheet metal screws, would likely be way cheaper.