
Hi & your right about John, he certainly knows what he's talking about.
I think it's great that you're considering rehoming an older dog, I agree with Debbie it would be good to start from scratch & bring up a pup just how you want to, but if everyone did that who would rehome older dogs in rescue? There are some lovely dogs that go through rescue & quite often through marriage break ups / working hours / new baby & so on, so it's not always behavioral or health problems with the dog why they need a home.
I think Mattie who posts here is involved with Lab rescue.
Good luck. :)