I have an idea for a kitchen appliance. How do I go about turning it into a real product?

• Should I hire a mechanical engineer and get a CAD design out?
• What about the electrical components? Do I need to hire an electrical engineer? Should they work together or separately?
• Should a patent be filed during development or only after the product is ready?

I can go on and on. I think it’d be easier for me to hire a company that provides end-to-end services. How do I find these in the US and/or China?

Any help would be greatly appreciated.