I see a very sweet dog who likely has a lot of love to give. No doubt he'll need some time to adjust. It's likely he'll never be super outgoing but that's not a huge deal. We had a girl once who was timid around people (fearless with other dogs). I'd joke by telling people she had just met, and was very wary of, that she had been abused as a puppy. When they'd ask what happened, I'd tell them that as a puppy she had gotten chicken rather than beef -- which was actually the truth. The point being that some dogs are naturally less outgoing than others.
Really was never a problem. Unless you're showing, your dog doesn't need to be uber tolerant of being handled by strangers. You might want to think about using a crate. Might help keep him calm and spare you some chewing or mistakes during the adaptation period.