Don't fear it, just do it.
There's is always an element of stress involved when you start a business. You need to find who needs your services (you probably have an idea who they are). At first selling your services is the key, actually selling yourself is the key. You seem to have a great smile and plus you are honest, so people will love doing business with you.
So to start, remember that selling is your primary job (you need the customers). Once you've pinpointed the demographics of your customer, attack like there is no tomorrow. Go see them, talk the talk, and some will buy from you....trust me. I've started businesses without even printing business cards and have gotten better money than those in regular jobs, it's all about confidence and selling.
However, before you sell, you need to know what other people charge for the same services. This is important cause at first you will need to underbid them. Be careful, do not underbid too much, just slightly under their price, and sometimes be ready to walk away (if they are cheap bastards). I've noticed that sometimes when customers care too much about the money, it's no fun working for them cause they are too demanding. Work for those who like who you are and not your price, you'll have fun doing it and make friends in the process.
The important question is..."Can I deliver the product?". So in your case, you need to make sure you have the equipment to produce quality. And if not, you might need to subcontract some of the work, rent extra equipment, but never say this to your customer. They need to feel you are in total control. Keep the credit to yourself. But make sure you know your costs before you quote a price.
Always, and always, listen to what the contract requires, but return home to think before you give a price, especially if it's custom work, which in your case will most likely be 90% of the time. People who have money and want quality, will usually understand that you can't give them a price right away. Beware of those who want a price on the spot.
There's nothing mysterious about business, all it is is this. Find the prospect, do the work and collect the money. Skip all the SBA bullshit about a business plans and all the tralala, unless you need a loan. I've seen people waste enormous amounts of time trying to figure out a business plan, and never got in business. Business is about meeting people who need your services, so the only business plan you need is to know who those people are. You'll have plenty of time to figure out the mechanics of business as you go.
Just go get the money. And please, don't be afraid to ask for a retainer. It's part of doing business.
Roll up your sleeves, meet people and you'll soon realize there's was no mystery to the whole thing.
Good luck and have fun.