I'm pretty out of the loop when it comes to laptops, but I think most of the components inside one are proprietary. I think you'll have to go through the manufacturer to get a replacement. I might be wrong about newer laptops, but at least that is the way it used to be.
99.99999999% of the time, you can just go get a 2.5'' hdd and put it in there. Though sometimes it isn't easy to actually get to the hard drive, it's almost always possible
As far as transferring the data from one drive to another, iGuess is right. It's not that hard to do, just time consuming...
Cloning from one drive to another (which is what iGuess was talking about) is hella lot faster than any other method of getting Windows and all your files onto a new hard drive.
Yes the new hard drive will come with nothing on it. As said you can make an image of the current drive with something such as Norton Ghost or Acronis True Image, though they are paid software. NewEgg had a deal recently on Ghost but if you want somethign free you could try DriveImage XML though I have never used it personally. Then you would just need to expand the volume size to fill the remaining space with the new drive.
Or use CloneZilla (which is completely free in every sense) which does direct imaging from drive to drive as well as expanding partition tables to fit larger drives.