Diagnostic tools are suggesting my 27" iMac hard drive is about to fail. It occasionally has trouble booting so I'm inclined to believe the prognosis (Techtool Pro). It also seems to 'thrash' for no apparent reason.
Looking at various websites for replacement disks I see they say 'hard' for the task. Have any of you done done an HD change? I'm IT and technically competent (even built my own computers in the past).
Is this a DIY job or do I have to resort to an expensive Apple repair?
Sensible suggestions please.