Here's a url to read regarding hernia's.
http://www.showdogsupersite.com/kenl...umbilical.html
Everyone has given you good advice here - I feel you should contact your vet and discuss this issue as well as ask the breeder for the vet's name that is doing the surgery so you completely understand the situation.
You need to be comforatable with all of this. If you have any hesitation you need to discuss this with the breeder. Your pup has a genetic health gaurantee.
Good Luck!!