First, welcome to BPO! This is a great site and I can pretty much guarantee that anything you encounter, someone around here has been there! I'm Heather, Mom to a 2 year old Greater Swiss Mountain Dog named Ranger.
Lucky me, Ranger is in the full throws of his PIA teenage attitude! I am a huge fan of NILIF and repetitive obedience training. It puts Mr. RangerRoo right back in line when he starts feeling his wheaties! Also, as Tina said, a tired puppy is a happy puppy. Ranger is a totally different dog when he's been walked vs. when Mom has been a slacker and wants a glass of wine instead.
I promise you, that sweet laid back baby will come back, once he knows who is in charge...which NEWSFLASH Molson, ain't you!
Good Luck!