10 points!! What should I do about this dog?!! =[?

Okay, My dad's shop dog died, his name was Bo. The shop I am referring to is a Big shop with a fireplace, and on the outside of it is a big run. it's probably 70x12 feet. We are wanting to get a new dog, and since I volunteer at the animal shelter, I showed him this beautiful puppy. We decided to take him on a ride and see how he got along with our Blue tick hound, Gus. He did great! But when Rock, my pug, saw him he started wagging his tail and Rock bit his weiner, lol, and the puppy growled and tried to bite Rock. So my dad said " We are not getting a dog that will bite my dog!" But it was Rock's fault! So we took him back to the shelter, and I felt really really guilty! The next day, (today) I said Dad, we can probably train him to not hurt rock and he agreed. But then ANOTHER problem came up. The shop is a MESS! He said it would take him a week to clean it up, and I offered to help. But he said it's just not the right timing. I'm SOOO sad! I want this puppy for me and my dad sooo badly! I don't know what to do! Sorry this is so long! =[