I just did this on my 2452tochange the shift cable.
The boat has a access from the rear of the control box thru the starboard seat pedestal.
The side mount merc 3000 has a plate which can be opened on the outside. Remove the screw holding the shift lever to the box. pull the shift lever out. The push button for throttle only must be pressed an the shift lever at 11 o'clock before doing this.
Behind the plate you will see 6 bolts going thru. Three outer ones hold the box to the side panel, other three inner ones hold the box to the mounting plate, called a "bezel" in the book. Remove these and the biox is free and can be lowered to work on it. Note: the wiring to the control handle trip and tilt switches have a plug to free the box.
Mow the switch is in plain view. With a friend working the rear of the side panel, and me in the wheelhouse, this took about a half hour. And, I never had done this before. here