I'm sorry to hear of the loss of your other budgie
You're right that this little one is still very young. However, he will begin to settle in soon. Playing soft music in the background, covering his cage on three sides, and sitting by his cage to softly talk to him will make him feel more at home. After two weeks, he should be more settled in. During the two-week period, don't try to touch or tame him
Best of luck with your new baby!