30 minutes - 2 heures
My Macbook Pro had a mere 500 GB HD, and was full. I couldn't find enough stuff I wanted to delete, so I couldn't even upgrade anything.
The replacement of the HD with a 1 TB HD was perhaps the easiest "repair" I've ever done. I now have hopefully a while before this HD gets full.
Before replacing the HD, I cloned my current HD with SuperDuper to an external HD, then booted my Macbook from the clone and copied the clone to my new HD. I then rebooted from the new HD and am off and away.