ORIGINAL: Bugflipper

They are never too old. Just focus on obedience first and play fetch for fun. Teach her to sit, stay and come. When she gets that work on combining the retrieve with that. You have her sit, trow the bumber with hand on her chest, command stay then quickly excitedly say fetch it up and point the arm holding her back directly at the bumper. Use come here when she gets it then sit when she gets to you then release when she sits. When she get's all of that increase the time between throwing and the fetch command over time. Then work on heel and lay down.

By that time you will have here conditioned to you being the boss and you can work on tougher things to compliment what ever fashion you want to use to hunt. Just be patient, shower her with praise when she does even the simplest commands at first and make every training session fun. When she fully understands and you are just going through drills to keep her accustomed to the basics a simple pat on the shoulders and good girl will do. Watch her throat, when she swallows that means acceptance and comfort in the situation.
If she gets bored or unresponsive because of excitement just end the session and go about your business. When she is just learning the basics. She will learn that training time is the best time to bet praise and have fun, she will be eager to learn anything to get your praise. Labs are so eager to please obedience is very easy with them and they generally wont challenge your role as the leader. They do get wound up and side tracked. That's when the firm sit command is given to get them back into a calm submissive state after they fully know the basics.
Blessings