A chin implant will not improve your snoring or sleep apnea. Since the implant is merely placed over the bone of your chin it does nothing to improve your airway.
Sliding genioplasty surgery is a type of chin augmentation procedure that can help with snoring/sleep apnea. This involves cutting the bone of the chin, advancing it foward and using special titanium plates to secure the bone. Some of the muscles of the tongue attach to this bone which allows the tongue to be advanced foward a bit with the surgery. I do this type of surgery in addition to chin implants and have had good success in treating snoring/sleep apnea with it (you can check out my website gallery for examples).
Even more extensive surgery would be an orthognatic procedure where cuts are made in the jaw (lower and/or upper) bone further back allowing even greater forward movement of the tissues. This type of surgery is generally performed by oral surgeons or craniofacial-trained surgeons. You would want someone with specific orthognatic surgery training to do this type of surgery. It is a powerful technique that can also be used to reallign someone's teeth if their bite is off.
Web reference: http://www.drlamperti.com/treatments/chin-augmentation