Stacking Washer/Dryer in T40A

[Sparky]

Good Morning
We have a new to us 2006 T40A and the one piece washer/dryer combo has been removed by the previous owner. We could put it back however would like to install a stacking unit. It appears however that although all the hoses and vents are in place in the lower cabinet that the upper cupboard is not as deep as the lower part so this may be difficult. There is a panel in the rear of the upper cupboard that I am looking to remove - Does anyone know what is located behind the panel?
We are new to the unit and would appreciate any help. Thanks Bill