older and younger dog

Question
i have a seven-year old spayed female Aussie mix (Aussie). her friend of six years (a dog) died in the spring.
i have begun to introduce her to a 9 month old nurtured male Australian shepherd named Arlis.
Arlis spent five days with us a month ago.  It was a very stressful time for me until the last day.  Aussie (the 7-year old) was fine with me petting Arlis and feed time was not too bad (i put down Aussies food first and had Arlis sit, then put down his food).  The difficult and stressful parts were toys, bones, and Arils getting in Aussie's face to play.  
How do I handle the toy/bone/in your face situations? Aussie growled alot and snapped alot.    i took all bones and toys away and only let them play with what "I" wanted to play with and gave bones/chew toys only when Arlis was in his crate and they were separated.  
I am bringing Arlis back home tomorrow and need to know how to handle this situation so I do not get stressed!!
Do I tell Aussie-the older one- "NO" if she snaps at Arlis for grabbing her toy/bone/etc?  Or do I let them "work it out?"  what about when Arlis gets in her face and she snaps at him?  Do i allow Aussie to have control of that?  Another time they were playing tug with a rope.  Arlis inched up on the rope and put his paws over it, like dogs do, and Aussie flipped out on him, snapping, and he went down in the passive position.  
I get scared and nervous when this happens and I am sure the dogs pick up on it.  
thank you for your help.  
Lori

Answer
Hi Lori, You are his Alpha dog. It is your job to correct them when they growl or argue by saying "NO GROWLING", or "BE GENTLE" so you establish the fact that you are the pack leader, Aussie is second and Arlis is next. If you must put him in a sit/stay or down/stay and if he does not behave roll him over, glare in his eyes and pinch at his neck. He must understand that you are the boss and he will respond to you. Aggression begets aggression,so a slap will not get the point across. They will both soon understand the pack order, but they must go through it with your leadership. Many times if you leave several bones or toys about, there will be snapping a bit, and it is okay as long as it does not get violent or make contact with teeth. I correct a new member to my pack with the "GENTLE" command and a hand signal. Because Arlis rolled into the submissive position during the rope tug game, is a good thing. The snapping is hard to hear, but you don't have to intervene unless teeth are concerned. Don't stress or your nervousness will be picked up by them. You seem to have a very good understanding of canine behavior, so do not worry. Leave me feedback and nominations so I will know  how you are doing with them. It is the only way we know if we are serving you well. Tell me how they are doing with a follow-up. Warm Regards. Susan