As per the title, my MBP is having some issues. When I start the machine and login it hangs on a completely grey screen. I cannot get the machine to boot into safe mode, or recovery mode or access disk utility. It literally goes from login to grey screen. I have been advised this could possibly be the hard drive. Does this sound likely? It had crashed when I upgraded to High Sierra and I had done a reinstall from clean which had got it working again until this. If I buy a new hard drive. How do I boot to format the drive and install High Sierra with a completely new drive? I am thinking if I change the drive it should be to an SSD. Any recommendations on models? Do I need to do something about TRIM? I have heard of that but no idea what it is. Lastly....thoughts on doing this? Is it likely to be the hard drive? Worth fixing or best to confine the MacBook to the grave?