I currently own a 450B and have pulled the clutches a couple of times.
The tracks on a 450B does not have a split link or key. You have to manually press one of the pins out to split track.
Thats the hard part.
Remove the side upper arm rest assembly.
Drop off the drive sprocket.
The final drive spline is behind a cover plate just inside of where the drive sprocket was mounted.
It slides out when the cover is removed.
Then you can get to the clutches, dry type, and remove from the top cover hole. Clutches remind me of a multiple disc auto clutch assembly.
The only other part to remove before pulling the discs is the brake band. That's a no biggie.