7 year old female German Shepherd meeting 13 week old male german shepherd.

Question
I have a 7 year old female german shepherd who has always gotten along with other dogs. She would play with dogs and cats, until she had puppies about 4-5 years ago. After she had puppies she became quite aggressive and overprotective. I bought a 13 week old german shepherd last night, male of course, and now I am scared to intorduce them. When the male was brought into the house, she was sniffing him and jumping towards him, since he was being carried. Nowhere did she show signs of aggression. Her tail was wagging, but, at one point she did growl. Now I am not sure if this was such a good idea. We have kept them seperated, due to the fact that we're scared of what could happen. This morning we took the male to one side of  the gate and the female to the other side of the gate. We let them meet, sniff each other and even lick each other. There was no growling or barking, just a lot of wimpering and the female was digging under the gate to try and get at him. What would be the best way in helping them meet? Would it be to put a muzzle on her and let them around each other, but then I fear what could happen when the muzzle is off... or, what else could we do? Put her on a leash and see how she reacts towards him? Any adivce would be greatly appreciated.

Answer
The fact that she didn't react badly when separated by a fence was good.  It's normal for a female to become aggressive to protect puppies, but if she was not aggressive prior to that, and the pups are weaned and gone, then you may not have a problem.  When I try introductions, I do them on neutral territory - not in the older dog's home turf.  Dogs are leashed, but the leashes are loose, drooping on the ground, so neither dog feels trapped.  If they sniffed already and "licked" (that's a sign that they meant no harm), then a more intimate intro is probably ok.  Sure, muzzle the old girl if you think you need to, it will probably keep you from transmitting all your anxiety right down the leash, but make the intro fun!  If you really are too nervous, get a local trainer to help you.