You'll need an external HD case (bare) to house your new drive in then have this plugged into either a firewire port (best) or USB port on your system before you open it up.
Using Apples Migration Assistant App (which you have in your app folder) copy over your OS, settings & all of your files over to the new disk. Then to double check things go into your systems preferences and alter your boot disk to this external drive and restart your system at that point the external drive should be the top most HD in the finder.
Now shut down your system take it apart swap your drives put the system back together and restart. Your new drive should be all set.