I am so sorry about Chunk's diagnosis, but I think you'll be surprised how well he adapts.
I belong to a canine diabetes website (Lady is a diabetic) and since most diabetic dogs go blind, we hear a lot of stories about blind dogs. It's always the owners who are most upset in the beginning, not the dogs. After a period of adjustment, most people report how amazed they are that their blind dog can still get around so well. We have one girl who was able to start jogging again with her Lab by tying his leash to her waist!
Living With Blind Dogs is a book that many people rave about
:
Amazon.com: Living With Blind Dogs: A Resource...
This website is also a wonderful resource:
http://www.blinddogs.com/