The new drive is fitted into this enclosure. You would have to download a software cloning program to the old hard drive, many of which are free, and this would do a complete copy (CLONE) of everything on your old drive, including your Operating System to your new drive. You then remove the old hard drive from your laptop and replace it with the new hard drive from the enclosure.
The LINK I have given you above for the Hard Drive Enclosure is one I have myself - it is quite sturdy - looks like black plastic but is actually metal. I have just recently done a HDD Upgrade (160GB to 500GB) for a friends laptop which took just over 2hrs.
If as you say this is a refurb then it should only have the OS on it and maybe a few free programs installed so shouldn't take long to clone.
The choice is yours - unless you prefer a CLEAN install.
what's the link to the one you suggested with the 1 TB HDD , no i didn't shop about just looked on pc world i liked the white i dunno why i know it looks like cheap plastic but still i might go for tbat as its only £20 ish more