I echo Karen when I say thank you for taking in an older dog, did you get him from a shelter? The only reason I ask is because most shelter would have neutered him before adopting him out. Just curious.
As far as neutering changing behavior problems... I believe it can help, no matter what age.
An intact male can smell a female in heat a few miles away which could make some males aggressive.
There's also possible health issues you can help avoid by neutering your dog. You would decrease his chance of testicular and prostate cancer if her were neutered.