It depends on the adult dog you already have. Dogs are territorial animals. You will be bringing the new pup home and into your adult dogs territory. With some dogs it's not a problem, others will fight like hell to protect thier territory. You have to figure this one out based on how well you know your dog. Another thing you should be aware of is that your adult might be jealous of the new pup. If so, then he may get aggressive towards the pup and the pup could get hurt. As far as the sex of either dog is concerned, I doubt that it will be much of a factor. As far as getting the dog neutered, Get it done as soon as the vet reccommends it be done. Unlessone is a professional breeder he has no buisness breeding. Too many dogs are the result of indiscriminate breeding leading to health problems as well as temperment problems. There are many dogs in this country that need to be adopted because they were accidents and nobody wants them. Alot of this would be avoided if breeding were left to the individuals who breed professionally.