So sorry to hear about your baby. But please know that this new baby is 1) not a replacment and 2) nothing you should feel guilty about.
We got Ozzie a week after putting our first Yorkie down. Too soon? Maybe -- but Ozzie didn't think so. He is my best bud and one of the greatest gifts ever to come my way.
Sounds like you've been given a similar opportunity. Don't pass it up.