I'm confused. You managed to undo the cables to remove the shifter base, but don't know how to put it back together?
The round bits on the cable, twist the plastic nuts in opposing directions to loosen them.
The cable ends are a ball and socket. Pry to remove and push with force to instal.
Oh wait, I got what you're saying now.
How do you remove the shift lever.
The black portion is a rubber gasket of sorts. Underneath it is a 2 piece hunk of plastic that acts like a bushing for the shift lever.