I was just going to write the same thing: if you hired someone you trust, trust that they are going to do the job well.
I like the three month transition plan given by Capt.DrumkenBum below, but I'd also like to add that you should try not to take too much pride or ownership in your existing systems. If new guy is going to change them and has good reason, be supportive, even if it feels personal. New guy has to run the ship now, let him run it the way it works, and works for him. Even if you have to say goodbye to one of your own creations and ways of doing things.
Having been there myself, it isn't always easy to go from micro to macro (or trusting someone else to handle some your old micro), but try to think of it is standing on shoulders instead of standing on toes. Now you have bigger challenges to face.
I'm sure there's a John Travlota joke about letting go to be made here...