I have actually googled this before, but new pet stress/regret is a real and common phenomenon! It’s a big change for you and the other birdie in your life. It’s why I keep shying away from committing to a second bird myself now that Sammy is in her new home - I KNOW those first few weeks/months of having another bird in the house are going to be difficult and his highness is not going to take kindly to it!
All this to say; everything you are feeling and experiencing is totally valid and normal, and in all likelihood it will get better. I look forward to months from now when your feathered friends are settled in one way or another!
I find it helps in this type of situation to consider what the worst case scenario could be (for me, it’s always “both birds hate each other” or “both birds have formed an alliance against me”, but leaning toward “hate each other” LOL) and how you will handle it. Then I feel like I have a plan and even if the worst happens, I am prepared for it.
I hope Rico comes to love his little “Corny” sibling Cricket. Even if they never get along, it’s enriching for them to have company.