Just because your done and bored with her isnt a reason to get rid of her. You made the decision to get her in teh first place so you should get rid of her. And btw if she's not AKC or have any papers, she's not worth that much.
Don't just sell her because she doesn't do what you want her to! All dogs get older, just like humans. You have to be the one to get her up and doing stuff. You can't just expect her to have the energy of a pup all her life. You should've though about that before you got her.
If the dog is lazy it is partly your fault golden retrievers need to be trained for at least two hours a day!!! If you are not able to give the dog that kinda of attention then you should not have that breed of dog. If you no longer love or want your dog contact a golden retriever rescue organization...