A picture up my exhaust - what am I looking at?

[imjus4u2nv]

Had to drop lower unit (first time for me on a yamaha) to replace the waterpump (see my other post - was overheating).
Wondering if any maintenance to do while lower unit is off and I wait for parts, took a peak up exhaust and noticed difference from port (looks greasier) the starboard. Should I clean the exhaust at all (rub down, clean etc).
Also, when I out the lower unit back om the black gasket/oring looks pretty rough. Does that black oring pop out? And is there a part after/under that? I cant find a schematic.
Any help as always is appreciated.

 

[imjus4u2nv]

It appears to be these two parts (if look careful can see part of the metal clip/ends in the pictures). I dont see a rubber oring though in the schematic, and from the picture on another site looks like that isthe rubber "oring". Anyone ever mess with replacing before - really would prefer not to open can of worms unless necessary. Not sure if can make do or easy fix (ha).

 

[Fishtales]

shaft and water? hard to tell from pics.

 

[imjus4u2nv]

Turns out for sure it is the driveshaft bushing (the pictures from my last post), I got the split ring key but cant slide the bearing out.
Ordered a blind hammer puller and the bearing/washer. Will report back afterwards.