Unfortunately, the reefers in earlier AS's were attached witha piece of Aluminum metal that is concealed behind the interior side wall on either side.
You may have to remove some interior components to include but not limited to credenza, interior wall, closet, to get to the screws.
I have had much better luck with Units since 1979, all screws were accessible from the front and rear (access panel)
Did I mention of the five AS's I have had, I had to replace or repair four of them? Seems that Fridge replacement is SOP.