I just wanted to add to this guide. I tried to disassemble it as well. I started by removing the top. As you described I could not find a way to remove the plastic top without damaging the plastic clips. Once the top was removed I was able to remove all the internal components without any issues. To remove the hard drive I unclipped all the plastic clips on the inside of the frame, lifted up the frame and slid the hard drive out of the back of the case.
I have the 8TB version. It uses a Seagate Archive HDD based on SMR technology. It is not fast but good for inexpensive mass storage.