I have not seen nor installed one of Stu's fan kits but I have made a couple of similar units myself. It is necessary to remove the refrigerator if you do not have the double side vent doors, i.e., you have the roof vented design.
If you are handy, it should not be difficult to figure it out. The temp switch is mounted to the piping with a strap just before the fins or on one of the end fins with short screws. The housing needs to cover the fins on the upper section of the cabinet back and you will need to eyeball attachment points. Assume the supplied housing will need minor cutting/adjustment to fit your particular refrigerator. You can safely screw anywhere in the back with 1/2" screws to secure the housing where the shroud contacts the back.
The power wire should run from the refrigerator switched 12v
connection to the temp switch, then from the switch to the the positive fan wire. The fan ground wire should run back to the negative 12v
connection next to the positive which you used to begin the run.