Product review (5 stars): Works great for stacking a Duet washer/dryer combo
This kit is only for the Duet, not the Duet Sport.  If your dryer has a separate cover for the hinge, an outside handle (basically a plastic rectangle facing you on either side of the door) and doesn't have a single piece of trim surrounding both the door and the cycle selector, you need a different kit.  This is just a trim piece to cover the right side hinge cutout on the Duet dryer door.  And yes, it's overpriced.

If you want to try reversing the door without this kit, the angles on the existing trim piece are only off enough to be noticeable and don't affect its operation.  The dryer would also work fine without the trim piece but it looks unfinished with the door open.

Reversing the Duet door requires removing it from the dryer (5 screws) and then separating the door sides (8 screws) to move the hinge (4 screws) from left to right.

The lozenge-shaped white piece in the photo is a mylar sticker that covers the screw holes on the right side of the dryer and matches the same thing that is permanently stuck to the left side.  I didn't get the trapezoidal black piece in the photo but it is probably a new finger pad for the handle part of the door and it doesn't need to be replaced.

I didn't need any shims to get the door to line up.  The hinge is pretty complex and the piece I'll call the "tie rod" on mine is worn to the point where I need to press the top and bottom of the door (or slam it) to get both catches engaged.  This didn't improve after reversing the door but the hinge is too expensive to replace, so I just push on the top and bottom before drying a load.