I had Lady first and brought a 3 year old, Gracie home when Lady was 6 months old. So not quite the same situation. It took a couple weeks for them to start getting along but now they play and snuggle up together all the time. Gracie even helps to teach Lady not to be so rambunctious. But as much as they get along, I'll always be the favourite! Don't be worried about that. It might take a bit of adjusting but I think having a second dog was a great addition and it's not all that much additional work. You'll just have to take time with each of them especially to train a new puppy. Koda will probably love having a puppy around to play with .
Lady (1.5 year old tricolour) & Gracie (4 year old blenheim)
"Happiness is a warm puppy" - Charles M. Schulz