How to replace hard drive without reinstalling the whole system?
Have you considered cloning your current hard drive? With a utility like Carbon Copy Cloner (which you can use for free for 30 days, I think), and an external interface for your new hard drive (USB, Firewire, etc.), you can clone--i.e. make a bit-for-bit copy of your operating system and installed programs--the drive that's currently in your computer. Then, when you install the new hard drive, the computer should see it as the boot disk and everything should pick up exactly where you left off--just with a lot more storage.