I think they start to lose them around 4mths of age - and usually should have lost them all by the age of 6 or 7mths. Some puppies will retain their puppy teeth and they will need to be pulled to prevent problems down the road. Oscar ended up with two rows of teeth (looked like a shark) and when he went in for his neuter they removed FOURTEEN teeth!
Encourage your puppy to chew chew chew and play games of tug with them to encourage those puppy teeth to fall out on their own so you dont have to spend a fortune having them removed!
As far as biting - that is all part in parcel of how you train him. Teach him early on not to bite. Some people on here have tried yelping when the dog bit them too hard and after a few times, the dog stopped. It makes sense, since that's how dogs let each other know that something hurts right? You could give that a try. If he doesn't quit... well, at least the adult teeth are much duller than their puppy teeth so it won't hurt as much!
