Training a Lab

[paublo25]

Well I have a 1-1.5 year old 80lb male black lab that showed up at my house 3 weeks ago. Tried to find his owner or a new owner with no luck and now my wife fell in love with him so we are keeping him. I've got him to sit and stay about 2 weeks in but every time I throw something he just wants to play but when I put a 40' rope on him he thinks he's punished. Also he wont jump in the back of the truck and just puts his front paws up and then just looks at me. Every time he is in the back of my truck he will get so excited he'll piss and ***** in the back. Now I would like any advice on whether I should send him off or if anyone has a way for me to train him to retrieve. He will hunt some but will be a house dog first so I don't want to break the bank on him. All I would like for him to do is retrieve and bring it back to me. If he would be to far gone to train I will just put more effort into finding him a new home. Any advice will be greatly appreciated. Also forgot so say that I live in Rayne but I have no problem traveling if I end up sending him off.