If you had solid silicone implants, removing them is fairly easy. They can be removed trough the same small incisions on the side of the mouth by sliding them out. Your lips obviously will get small and should return to the way they looked before you had them augmented.
If your lips are hard from having silicone injections, then removing them is much more difficult and can be a problem. That is why you should only use solid implants or inject the lips with a temporary filler like Juviderm or Restylane. Using your own fat to fill the lips is also a good option. Injection with a permanent substance is never a good idea anywhere in the body.
Web reference: http://www.drhamawy.com