1 Drill a hole through the plastic outer in line with one of the holes in the shiny plate behind if possible
Screw in a big self tapper to catch the hole edge behind and pry against that self tapper and lever against a small wooden block against the engine
Try to avoid prying on the edge of the recess for the sightglass!!!
2009 is showing the steel circlip ring
LINKY Parts 2 & 3 So have a good look for that before you go hauling and pulling anything out
Take the old one out!
Clean the recess!
Slightest smear of oil to help it go in and away you go
(Remember to check for an inner edge that stops the seal falling inside the engine!!)