I had a 3 year old shepherd female and got an 8 week dobe puppy - same fear. What worked for me: -
I took the shepherd with me (I have an SUV) - and I had the breeder hold my puppy while I opened the back door. T he GSD growled because she is naturally protective of the truck, I told her to leave it.
I put the puppy in a crate in the truck and drove home (1 hour)
During the drive home, the GSD sniffed the cage and got used to the idea a new member of the family was here.
When I got home, I took ALL dogs (acutally I have 3 and brought the old boy with me too) - anyway, I took all three into the house at the same time, I carried the puppy at my chest from the car while I walked the other two on lead.
It worked - and I think its better than having your dogs at home and THEN bringing the puppy in.
Good luck
PS: What I have also found is the issues a dog have surface quickly - or not at all. If your Aussie is nasty, take no chances and keep them separated and give them time to adjust. Dogs are individuals - and judgement must be applied.