Access to the overboard discharge is easy. Removing the seat not so much, thought I’ve done it.
At the end of the “cave” there is a rectangular door in the wall that just pulls off. I think it’s secured with Velcro if I’m remembering correctly. Behind the door is a valve with a lever. It is not a Y-valve, simply on or off. When off, the macerator cannot pump overboard (but you can still use the pumpout port).
You can service the outlet by just pulling it out from underneath the dinette table. If you need to get at the wiring behind, removing the seat won’t help you; it is resting on a fiberglass ledge. If you remove the whole vertical panel at the end of the cave (I believe it has two screws top and two bottom), you can reach around and get at the wiring to the outlet. At that point, if you wish, you can remove two screws at the rear of the wine cooler and then pull the wine cooler out to give you increased access. If for some reason you still wanted to remove the seat, it is secured with screws that can be accessed once the wine cooler is out.
John