miniature schnauzer timidness

by Mac MacFarlane
(New Jersey)

We lost our 14 and 1/2 year old schnauzer to cancer about a month ago. He was a great dog. We were all devastated, particularly my wife.
As a result a week ago we purchased a 7 month old miniature schnauzer from a breeder. While healthy and very lovable when held he is very timid. He withdraws to my daughter's bed until she comes home and doesn't respond to a call.
When she leaves he howls for a little while. You can hold him for a while until he's ready to move. When you then approach him he softly growls.
We took him outside to the back yard and he stayed in the corner or under a chair. We tried to walk him with a vest harness and he was reluctant to leave the house. We've been very patient but he obviously has trouble socializing. He was not crate trained. The breeder said she kept him in a fenced in cement run with doggie door access to his living area. He is starting to become less withdrawn.
My question is what is the best method to help him become more sociable and ready for more training? We never had any problems with our other dog which was 12 weeks when we got him and crate trained.
The comparison is inevitable as he always was bouncing out to greet and love my wife even as a puppy. As he is very loveable I'm sure he will adjust.
Your response would be appreciated.
Thank you Mac MacFarlane