1. What size and spreed will the new drive be? Al larger, faster drive may improve performance.
2. How is the old drive removed and replaced? Many makers offer guides, and this is usually a matter of just a few screws and the right screwdriver, but do your homework before starting.
3. How to re-install the OS? You'll need a restore disk of some kind.
4. Once the OS is re-installed you'll need to reinstall all your programs, virus program and Windows updates.
5. When this is done, consider getting an external drive for an imaging and/or backup program.
Enjoy.