ok so i removed my shifter and there was a black plastic ring piece with a thin metal ring attached to it.

what is this piece called? because the metal ring around it is bent akwardly. its like warped

and what kind of gear oil should i put in it? because there is nothing but black goop in here and it looks nastay.

im asking these questions because after putting it back together my gears can now slip in and out of gears without depressing the cutch.

is it somehow related? because before i did this my gears were working just fine.
any help would be nice

 

wave washer is deliberately wavy