Congratulations. I got my new 19 several weeks ago and I couldn't be happier with it. Just like my wife's 26, it has performed perfectly since day one.
I took the gun shops advice and just went out and used both guns and we've had no issues. No special ammo, no break-in process, just bought ammo that was available, shot, and always cleaned them after a day at the range. Just like our Toyotas, just use them and take decent care of them and they will perform well. That has been our experience with the 2 year old 26 and it looks like the 6 week old 19 is following the same path.
Good luck and enjoy it.
Gen 3 G19
Gen 3 G26