How to integrate a new dog into the family advice!

I have a 2 year old male golden retriever who is not neutered. He loves attention and will push any other dog out of the way if he sees that they’re getting attention over him but he’s never been aggressive to other dogs. My ex did have a female Aussie golden retriever mix when we lived together and they did great together. And since her and I split up he’s just seemed so bummed out and I really want him to have a new friend. A co worker of mine has Aussie/great perenase and German Shepard mix puppies and I’ve fallen in love with one of the male puppies. Needless to say my golden has been absolutely babied and adored his whole life and I’m looking for advice on how to introduce him to a new member to the family. Thank you to anyone who has some words of wisdom!