5 - 15 minuten
I got the gray screen with the "FOLDER?" icon. I then booted from the install disk tried the disk utilities to repair the drive but got error message that it could not release drive. I then tried booting again from install disk this time the internal drive would show up but showed 0 disk size. So I ran other diagnostic and it appeared only the drive was affected.
I followed the guide on replacing the drive and it took about 20 min, everything went well and after replacement I installed the OS. Everything went well except after running for about 2 hours now I have a screen problem where there are wavy lines going through it and distortion of the colors. I have not determine the issue on this since I am still installing all my files, but I think it is either a display cable ground problem or bad cable.
Since I had my issue with the display, you need to take care when placing the display back in the case and to apply little as possible stress on the cables when disconnecting.
The Fixit guide is great with very good details on how to replace the drive and it took less then 20min.