What you are dealing with is a Labrador puppy being a normal Labrador puppy. My boy Brooks is now 16 months old, and at times he will still jump up out of excitement, and will still try to mouth my hands and arms, which is fixed with a stern "leave it". He and my almost 6 year old Lab Sophie also play very rough, lot's of growling and teeth, but it's only play.
Kimbers Mom posted this
Puppy biting! which details a lot of good information regarding this issue.
The first year or two can be pretty rough living with a Lab puppy, but with a lot of time, training, and most importantly, patience, you will have a great dog and loyal companion. I would also highly recommend finding a good obedience training class. You will learn the how's and why's of what you need to do to correct and prevent bad behavior issues.
BTW - What's your puppy's name, and we'd love to see some pics???!!!