Don't be put off by the stories. As Dee has just pointed out males and females can often fight also.
I have two females and so far so good. My older girl when I first originally bought Phi home had a couple snaps at her when she was being annoying but nothing in the past 4 months or so. They love to play now and are good friends. I think it also comes down to making sure YOU are the head of the family or pack leader which ever you prefer.
I agree with everyone else do not give either more attention than the other. Dogs do not understand why you are doing it. Better to spend equal time with each, feed them equally, give them treats and attention equally.
Good luck. In the end if your not sure at the end of the trial period it is probably not a good idea. You need to be absolutely sure that adding this particular dog to your family is right for you, your OH and your current dog.