Spend as much time with her as possible, im in the same situation. I have hounds, and they are a little rusty the fist couple times we go out, but they soon come around. they are 5,4,3 and still have pleanty of good years to come, so shes not to old.

She should still be trainable. No matter how old the dog you can still teach them new tricks, and in your case brush up on old ones. Ive seen it happen and just as long as you're determined youll be able to retrain her.

I don't believe a dog can lose its sense of smell, except form an infection, an injury or from old age. Just living in a house does not diminish any of a dog's senses. It does intensify its bonding with humans, and that is a plus for hunting dogs.

I don't know. Some Labradors can't wait for the opportunity to retire. If she refuses, you are finished. Good hunting Labs are extremely enthusiastic and can't wait to retrieve and you can't hold them back. This is the kind I have experience with. I had a very reluctant puppy, though, and he quit several times. But I also had an older dawg that got him re-interested. What I would do is try to get her re-interested on singles at short range with bouncing tennis balls, and then gradually increase the distance to maybe 50 yards. Then get some real pheasants and go through the whole routine. Get an assistant and shoot flyers. You can use an enthusiastic retriever of any breed to re-instill enthusiasm by example at this point. I have done this as well. If this doesn't do it, you have a cookie-eating kitchen dawg.