Needs instructions in replacing joystick cover

[Kurniadion]

I absolutely love my M3 and the way it looks, especially the white grey theme. I'd like to keep it nice however extended use made the joystick kinda dirty and a little stratched up. So I bought the original joystick cover and think that this is gonna be an easy job. Apparently not, at least to an inexperienced guy like me. I removed the joystick module's top 4 screws and apparently wasnt enough to get it open. I removed some additional screws on the left and still couldn't get it open.

Can anyone give me instructions how to do this, that is if you think this is recommended. Is it that complicated? Well, at least I thought it could be done without going to a repair center which means $$. Any help will be highly appreciated. Many thanks beforehand.