I'm not giving up my pooch for that long.
Does the dog stay there the whole time? What are the "basics" and what do they teach the him/her?
Well, I guess that depends where your dog is at when it goes to the trainer. The basics to me would be having lots of birds thrown for it, learn to heal and sit at your side no matter what, if you are into upland hunting maybe sitting to the flush, and to a whistle. There are so many different aspects to this, I guess you have to decide what you want out of your dog.
And yes, the dog would most likely stay at the trainers the entire time. My last pup, I sent to the trainer, I had them do the Force Fetch and Collar conditioning for me, it was 2 1/2 months, but she went Oct. and got her Back the middle of Dec.. she was 9 months old, so she would have been a little young for the goose hunting that I was doing, and I also Deer hunt a lot, so the timing worked out well. For me, I like doing the obedience work, and my newest pup, I am going to attempt to do the Force Fetch and Collar Conditioning myself. The marking work that a dog does, is also really enjoyable, but you either need a couple of helpers, or a sizable investment in remote bird launchers. Blind retrieve work is a good way to spend a half hour training with just you and your dog.
Lots of people who are into Field trialing and Hunt Testing send their dogs down south with a trainer every winter. It is good for them, cause the trainer is working with the dog every day, and they get to hit the Trials in the warmer climates.