I will third - or fourth? - that you go find the dog park threads and read them.
Your experience with your other dog is EXACTLY why dog parks are a horrible choice for EVERY dog of EVERY breed. Your dog was attacked by a dog for no reason - and it was injured and you were injured. That little dog could have done serious
damage to your dog, what if it had bitten her in the eye instead of the neck?
Unprovoked attacks can also create permanent dog aggression - even against dogs that they already "knew." In a dog park setting, other dogs can also decide to join in the fray, creating a rolling dog fight that would be very dangerous to break up, and possibly cause severe injury for the dogs and people involved.
I honestly think it's just a posturing thing, he makes a lot of noise and looks the part, but he has never left a mark on any dog he's tangled up with.
He honestly is a big scaredy cat when it comes down to it.
Which is fine, until flight is removed for some reason... be it a leash or being cornered by a fence or other barrier. If he ever needs to use "fight" the result could be very bad, the scared ones can be the most vicious when the time comes.
If he is OK, and his body language is good (and the other dogs as well), then we bring him in.
Take a look at this thread: viewtopic.php?f=19&t=23382
Remember that there are a lot of idiots out there who would
bring a dog like mine to a dog park.