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I wanted to share my experience changing the cooling fan on a C55 in case anybody else needs to go through this, I wasn't able to find info specific to the C55 when doing mine and it would have saved me some time knowing that the process is a bit different when it comes to the C55.
There are a few guides on how to replace the cooling fan out there for regular W203s and W209s, I liked the Pelican parts step by step guide for W203s and I believe FCP Euro had a video for W209s. The process is very similar for the C55, you have to remove the front part of the engine cover, the intake inlet tubes, the upper frame (it goes all the way to the front of the radiator), the hood latches, and the grille.
On normal W203s and W209s this would be enough and you would be able to pretty much just disconnect the fan (there is a connection on the side, that can be reached from the top and one under that is easier to get from underneath) and pull the cooling fan out, but of course, that would be too easy, not much fun at all. You can get the fan loose but it won't be able to get out because of the radiator hose, so be ready to get some coolant because you will have to drain the system. In my case, I took my car to an MB dealer to get a trans adaptive reset and they did a free inspection for me, the only "issue" with the car was that it had the "wrong" coolant, so I went ahead and purchased a 50/50 "blue" coolant mix. To drain the system you will need to turn a red cap that is on the bottom-driver side of the radiator, remember just turn it do not try to remove it, remove you overflow tank cap and wait for the system completely, go watch some tv or have a drink it will take a few minutes. Afterward, disconnect the hose from the radiator and bend it back this is a quick disconnect hose so just remove the metal clip and pull it out if all clips from the cooling fan are loose just pull it out and that's it. Now clip the new fan, connect it and put everything back together. Remember to fill the car with coolant before starting it, fill the overflow tank then start the car and keep adding coolant until there is no air in the system, after a few mins the new fan should start and you should be done.