R230 SL quarter window seal replacement

[W169A180CDI]

The beltline seal that runs along the bottom of the rear quarter window on my SL has gone baggy, leaving an area with a gap between the seal and window.
Thankfully a new seal is available as a separate part and I am considering doing it myself. Has anyone done this job, and if so, how difficult was it?

 

[mioba]

With these type of jobs, you can usually get an idea of how it fits by looking by at the new part and how it attaches to the car. This then gives an idea of how to take the old one off.