Allroad clunking and fixing it

[THEluke]

Hey, i got an audi a6 c6 allroad half year ago. Recently it started to make clunking sound, which comes from the back. I asked some passenger to listen where does it come from, all of them said that it is coming from inside the car 😀 i think i found the fault part but i am not sure how to fix and did not find any info online. So i think the rear passenger side strut tower support went bad. Now how to change it? Do i need to depressurise the system? I will be taking out the shock to change the strut tower. How does it go? 

Thanks for info