First off congrats on the new dog and I am very sorry about your older dog. You need to make sure you give the older dog more attention as part of the process. He may be feeling left out and is causing him to be depressed. The older dog should be fed, treats, pats when you come in first always, establish the pack order to the new dog. Try and do things with both of them together and do spend some one on one with the older dog let him know you are not replacing him, he needs you now. Good luck
A dog has so many friends because they wag their tails not their tongues.
R.I.P. Buddy 2002-2008 The best Mastiff ever.
Now owned by Clark the Crazy American Bulldog