That second part didn't seem to come through but in any case, if you have reason to suspect the hard drive, it is probably better to act sooner than later. I see it is a 2 TB drive. The cost of a 2 TB SSD plus the cost to have someone install it might make you question whether the money might be better spent at this time on a newer machine. Having moved from a 2017 27" iMac myself, it is a tough choice and with no seemingly no new 27" iMac likely, I went with a Mac Mini and a good 3rd party 27"monitor.