First of all, welcome! Unfortunately I don't have much advice on the aggression, but I am sure someone here will. I would make sure that you are the alpha. Do you handle his food while he is eating it? I did that with mine. That way, they know that the food comes from me, and I can take it away at anytime. I would take it away and then give it back with a treat. I would also put my hands into it while they were eating. If they snarled or anything, I would say very stirnly 'no' and take the food away. Some dogs are very protective of their food. I would feed Jackson away from the lab. Then, allow the lab to be in another room, but not right where Jackson is eating but within ear shot of Jackson, then within eyesight, but still in another room. That way, Jackson can get used to another dog being around while he is eating. Make sure you praise him a lot for his good behaviour, vocally and with treats. Once Jackson is OK with the lab being in another room, have someone bring the lab into the kitchen where Jackson is eating on a leash, but still keep the lab far enough away. Praise, praise and praise Jackson when he is being good. Slowly, start to bring the lab closer and closer. Always supervise and praise. Shelties respond very well to positive reinforcement and they want to please their human. Good luck. Oh, and we love pictures, so post some if you can. We'd love to see him!