Can anyone tell me how to replace a lazy susan? I'm not sure how to get it in and out of an assembled corner.
You can wreck it getting it out. You can put the pole and shelves together inside the cabinet. It takes three hands, a small exclusive vocabulary and patience.
You will need to know what size circle will fit in the hole. The height of the cabinet opening will dictate what size lazy susan will fit through it. If you are planning the pie shaped shelves you have a bit more leeway.
OR You could put a shelf in there and set two lazy susans on them. You'll have to put each piece in and lay it on the floor of the cabinet in the order you will put it together. On the floor place one lazy susan. On top of that lay one shelf or if the shelf is in two pieces but both of them on top of the lazy susan. Then put the last lazy susan on top of the pile.
Leave the bottom lazy susan on the bottom floor/shelf. Raise the top shelf and the 2nd lazy susan to the desired position.