HDD Part of Fusion Drive needs replacement (iMac 27" late 2015)

My iMac - Intel 27” late 2015 - stopped working and starting it in recovery mode showed me the following information:

I suspect my HDD part of the Fusion drive is defect because I can see the SDD part? (it has a 2TB Fusion drive)
How can I test this?

If I need to replace this drive, is it ok to only buy a new drive (the Seagate Barracuda ST2000DM008 3.5'' 2TB SATA III) or do I need something else? And will it automatically create the Fusion drive again?

I also read you have to break apart the Fusion before replacing a drive but that is probably not going to work anymore?

Thanks in advance!