A good link for retraining dogs like this is
http://www.ttlntl.co.uk they have a forum run by Gill White. There are lots of trainers on there that have dealt with (in some cases actually taken on themselves) dogs like you describe.
They will probably know of a GOOD trainer local to you. They also have alot of good articles on behaviour etc.
The other thing I would say is that alot of these trainers on TV are not as good as they may seem. You never see the dogs a year down the line for one thing, and you don't see the work they do off screen. Some of the methods they use only seem to work in the short term, or cover up more serious issues the dog has. Also, if you use some of their methods on certain dogs you can end up making the problem ten times worse! A dog will attack another dog for many reasons, it could be that it is itself fearful of attack and could be 'getting in first'.
To retrain a dog like this you have to know what you are doing. There is no quick fix.
Good luck!