Mike: has this lab been to basic obeience training with you??? If not, this is the first recommendation I would make. If you can find a trainer in your area who teaches basic obedience and who uses smaller classes, like no more than 8 dogs to a class, then you should go with that. My preference is for a trainer who trains to both hand and voice commands.
Unless, as Dave points out, your Lab has been abused, or is just not trained and shy, the basic obedience class will solve many of those problems. You will attend with her and then practice each weeks lessons at home for about 15 minutes a day. This teaches your pet that you are the master and she is the pet and also teaches her how to react to your commands. This is a real 'bonding' process with your pet and both you and she will benefit from it.
Labs are hunters and good field dogs. They make wonderful pets and hunting companions if they have had the benefit of at least, basic obedience training. Any dog will require additional training to get accustomed to 'the gun', for field work. I asked earlier about 'gun' training for my Standard Poodles and one of the other responders gave me a good tip - it's lower down in the forum. it may help. And by the way, it won't matter how old your pet is when you take her for training - with the proper type of training that give praise and reinforcement for proper behavior she will be a joy, and a lap lug, and a good hunting companion, and a muddy lap-lug and, if she ever finds a field full of cowstuff, she will be a real smelly, joyful laplug.
As Dave said, I would also recommend your wife attend and participate in the training of the dog. Animals respond to consistency and this will help. Wives also respond the same way. Just my two cents worth.
Mikey.