The answer to that is yes, it's a fairly simple operation. You access the drive bay by removing a few small screws on the back of the machine.
Make sure you get the right drive for your laptop's make and model, and proceed carefully. You'll obviously need to install an operating system on the new drive, so make sure you have the software available before you change drives.
You should also back up important data files from the old drive to CD/DVD, so you can easily transfer them onto the new drive.