5 - 30 minuten
My 250 Gb hard drive was 225 Gb full and I was getting I/O errors. Although I had two external backup devices, each with a time machine and bootable SuperDuper backups, I was feeling insecure.
As a newbie, I initially plugged the USB connection between the HD enclosure in backwards with the result that my computer (and another I tested) couldn't 'see' the new drive at all. Once informed of my error, this was easily remedied. Then I had a challenge getting my old internal hard drive to stay connected while backing up with SuperDuper - it kept hanging up. It probably took 10 goes over 10 hours to get it all done (it might have been quicker to use one of my backups). Then I checked that the new bootable version was working before installing. The install process was relatively easy using the great ifixit guide (I used an ice cube tray cavity to hold each set of screws as I removed them, which made reassembly very straightforward). The only glitch was that my Microsoft Office required the product key before it would work - I had to buy a new one. Otherwise all is good.
1. If you can, install your new drive in an enclosure so you can plug it in externally and create a bootable backup using software such as SuperDuper (assuming your old drive is still functional). Then test that it is working and all there before installing it.
2. Use a clean, dry ice cube tray to hold the screws - a new cavity for each batch of screws you remove.
3. Beware that some licensed software may require re-registration to work (e.g. MS Office).
4. Be equipped to clean out the inevitable dust while you are inside your computer.
5. I also viewed some YouTube videos of others performing the same HD replacement which gave me additional confidence.