Thanks to the suggestion by Fredoops, I bought the magnafine inline filter for my CL9 and have my mechanic replaced it for me today. I never done it before and watching him do it today I should be able to do it myself next time.

The only concern I have with this inline filter is its plastic cover and we don't know how that will stand the heat inside the car bonnet. Will that become brittle over time? The original one is metal. I do notice the label on the new filter mentions it should be replaced every 10k km, I'll probably keep doing a normal drain and fill every 10k and the same go for this inline filter. Just to avoid a few grand transmission rebuild fee

Am I too paranoid?

Hehe and the mechanic was wondering which was the flow direction too. He got it in the end (I sincerely hope so)