It's Time To Reclaim My Position

As the master of the house that is.
Before Cooper went missing, he was no where near perfectly trained. He would sit the majority of the time, occaisionally it took more than one time of saying "sit", he would sometimes "stay" but most of the time not, he would occaisionally "heel", and he had gotten past the chewing stage. He definitely needed training. Then, he went missing for 3 weeks and everything regressed.
He will not "stay".
He will not "heel".
He will "sit"... when he thinks theres a treat coming his way.
He is back to chewing on things. He hasn't destroyed anything of worth. Yet, but if he can get something out of the trash, such as an empty treat container, he will chew it up and will chew on USB and power cords that hang off the back of my computer desk. Also, he has started chewing on my hands and arms and on Sams ears and legs.
Like I said, what little training I had accomplished was undone those weeks that he was missing, and I take full responsibility in not correcting it the minute he returned. I've spent the past 2 weeks since he's been home being overindulgent and letting him get away with all of this poor behavior. Now, I'm paying the price in that he does not listen.
It's time for obedience school or training classes of some sort. It is time for me to reclaim my position as the alpha dog in this pack... as his master.
What I need help with is finding classes. Can anyone suggest affordable and effective training? Any opinions on PetSmart or Petco? I think he would do better with a smaller class since he does get very excited whenever he sees other dogs (he wants to play and make friends!!!) but I do think a class setting would be better than private training since we do need to work on his behavior around other dogs.