I posted a discussion thinking I would get a serious answer

I was hoping someone would give me some information about adopting a new puppy when we already have a 3 year old dog at home.

I can look up a ton of information but I want the real practical information from people who have actually been through it.

The problem I can see so far is that our dog is very jealous and feels like he has to guard us (myself, particularly) from everything.

Here's some of his guarding behaviour:
He won't let the cat near the bathroom door if I'm in there
He barks out the front room window, the second I set foot inside the shower and won't stop until I'm done
He barks anytime someone approaches the house
He won't let my husband and I dance - something we really enjoy - and tries to stand between us. He's even barked at my husband and tries to grab him by the feet and drag him away from me.
If we sit side-by-side, he jumps in between us

He's a loving gentle dog but he is huge and sometimes he acts aggressively and excitedly towards us. The reason I want to adopt another German shepherd is because I feel the dog needs to socialize with other animals and needs the opportunity to run and wrestle with something equally as strong.....I should mention that his brother lives down the road and although it's fun when they get together it isn't often enough or with any regularity.

I hope I explained the situation well enough because the vet suggested we get a Lab because of their gentle quiet nature but I'm really hoping to adopt another German Shepherd.