Mikael,
The rear main seal looks like you think. And if it was installed correctly, part of it will be exposed and you should be able to grab it with a pliers and rotate it out.
I attempted to replace the seal with the engine in the car, but abandon the idea and pulled the engine out. I just don't think the job can be done properly with the engine in the car. Pulling the engine and transaxle as one unit really isn't that bad of a job.
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