It sounds like you have a really big heart and want to help this new dog.
I've found that walking dogs together (one human per dog) can help them to get used to each other. It also kind of simulates being on a hunt together, so they feel like they have a common goal. Positive reinforcement and calm, happy behaviors around both dogs are important, too.
Some people are really big believers in the pack order/dominance theory, which may be useful for some situations. Unfortunately, it's a derivative of research that was really actually crappy - based on the behaviors of wolves in captivity. THose wolves didn't act like normal wolves, and dogs aren't quite like wolves of any kind. The dog social structures and behaviors are quite a bit more nuanced than the pop psychology versions you'll find on the Dog Whisperer or in articles about pack structure.
But I would encourage you to try different approaches and see what works. Dogs are unique individuals and don't always fit one-size-fits-all approaches. Also, if something feels yukky or just viscerally wrong, then don't do it, no matter who the "expert" is that suggests it. If you don't feel comfortable with something, your dogs will sense that for sure, and it won't turn out so well.
I really like this article: http://www.humanesociety.org/animals...g_new_dog.html
Also, this video shows some lead-ups to aggression between 2 dogs and might help you notice when one dog is upset before any fighting occurs: