I'm so sorry for your loss - please don't feel guilty! We all want to do right by our pets and all we can do sometimes is put our faith and trust in the professionals who care for and know our dogs. Having a dog put down is the HARDEST decision.
As for the new babies - if you can take two go for it! I would LOVE LOVE LOVE to have another yorkie (someday! when the time is right!). Does the price/lack of papers bother you? If it's just a pet, I don't think papers are a big deal at all - some people like to have them, just for the sake of having them. A new puppy can help heal your heart after the loss of another - imagine having TWO!!!
OH, and
Good luck in your decision!