I have attended several group classes, but myself have found that having a down-to-earth trainer evaluate your dog one on one has worked best for me. There IS something your dog responds to. It may be tiny peices of hotdog chopped up, or in my GSD growing up, it was the chance to chase a ball.
All of my dogs are rescued, and I also foster rescues, so it is not often they are under a year old. Labs tend to take a bit longer to mature (at least 2 years), but it is possible to get them under control, regardless of when you start.
What exactly is the problem? Housebreaking? I can give you advice on that front, as that is the most common problem I deal with in my rescues/fosters.
Do you have a crate? If not, GET ONE. It's not cruel...trust me it would be much crueler to rehome her because she is 'untrained' but not 'untrainable'.
Does she jump? Bark? Rambunctious? Give specifics and you will get lots of tips. In the meantime, check your yellow pages for dog trainers, or ask your vet. You want one that is going to teach YOU to train your dog using positive reinforcement.
You say you are at wit's end, but imagine how your dog feels. She's never been taught how to behave, and now she's in trouble alot but has no idea why. For all she knows, you are speaking Russian and she is from Japan! Once she knows what you want/expect, she will respond in the way you want. But...it isn't going to happen in a day or a week and probably not even a month. But you WILL notice little changes day by day. Short sessions (10-15 minutes) 2 to 3 times a day work best.
Your dog will understand YOU much better if YOU understand HER. I highly recommend this book
http://www.amazon.com/gp/product/034...lance&n=283155.
Good luck, and please please please don't give up on her yet. She's desperate to please you...she just doesn't know how.