I was in a similar situation as you.
Background: I run a content site. Millions of visitors. Needed to scale into a real business fhat need me.
1. Read. A lot. Whatever bits of advice I can give pales in comparison to true knowledge. Specifically:
a. The E-Myth Revisited -- understand that "running a business" is completely different that "doing the job." Look at systemizing and building processes so that a monkey could do it. Remember: a good business isn't one that requires good employees. That's a flaw in the system. A good business is one that can take mediocre employees and through a good system produce superior products. Think McDonald's SOP.
b. Delivering Happiness. Hire for personality, train the skill. I can't emphasize this enough. You can always teach people skills but you CANNOT teach someone to be a good person. I made the mistake of hiring good writers, regardless of personality. The culture was horrible -- people were selfish, the culture was a mess. Eventually I fired everyone and started from scratch. The second time I did it the right way.
c. From Good to Great. Another culture book about building a sustainable business. There's two types of leaders: 1. Those that plan a direction, then find people to do the tasks and 2. Those who hire good people and then figure where to go. In 1. you're screwed if it doesn't work out as you planned. It never works out. In 2. you don't know where you're going but you'll eventually get somewhere good.
2. You'll need to beef up a different set of muscles. Yes, you're good at "doing the work." But you'll need to be good at "building a good team." Think of your role as being a coach rather than a player. Hire slowly, fire quickly. Spend your time hiring well.
I hate to cut it short but I'm typing from an iPhone. I run my company remotely. But really, if you do it right, it won't even need you. Don't worry about keeping your "secrets" safe. The truth is, your system and processes are your secrets. Not your ideas or your code. Ideas are a dime a dozen. Execution is where it's at.