Looks like you have gotten some good advice here. To facilitate the desensitization process you might want to think about using some of the natural products available to take the edge off. The less your dog practices the undesirable behaviour the easier it will be to train out of him. There is one called Rescue Remedy which is pretty readily available and will help calm your dog and another product called a DAP diffuser (or something like that) which emits some sort of calming scent? I haven't used either having a couple of stoic spaniels myself but I have heard good things about it. Depending on the size of the dog they have something called a calming wrap (kind of like a baby bunting blanket) which is also supposed to help - while I'm sure they make them in large sizes, I just can't imagine trussing up a lab in one of those myself

Mel