Being able to sing and play music well is a talent. So is songwriting. Just because you have the talent to sing and play well doesn't mean that you have the talent to write the words or notes in your music, and that's OK. You can hire someone who does have those talents so that they can help you. In fact, you may even end up hiring one person to write lyrics and another to write the actual music.
When most people think of a flute, they picture a musical instrument that is metal and has a silver finish. Flutes can be made of different materials, including nickel and silver, but your local musical instrument store may carry flutes that aren't made of metal at all. You'll often find plastic flutes at these retailers. Plastic flutes are the same size and shape as conventional metal flutes, and you play them in the same way.