This allows for a replacement unit which might be larger.
Install a window air conditioner in the wall.
Allow several inches of the case or sleeve to protrude from the wall into the room.
Window air conditioners often come with a foam insulating strip.
Remove unit front cover and screws that hold the unit inside its case.
Pull the unit forward while an assistant holds the case until it is fully withdrawn.
Secure the side panels with screws.
Your appliances should also have come with an installation guide that you can tape onto the wall and trace its outline.
Extend the accordion panels from both sides of the air conditioner to the window sash track.
Then measure the width of your through the wall air conditioner and transfer that measurement to the wall where the studs were marked.
Install the case or sleeve into the opening.
Use a stud finder to locate two adjacent stud bays that will provide enough room for the opening.