Very cool project. To simulate the stars, I did a project with WS2812 controllable LEDs that were mounted behind canvas with small pinholes. You can make them all twinkle, change colors, etc. Check out the FASTLed library for lots of examples/effects.
Like others have said, start simple and build it up. Don't be surprised if you create many sketches along the way, each one doing a single thing or testing/debugging one component. Get it working and then incorporate it into your main sketch.
Those DFMiniPlayers are very easy to use. Note that you don't get much volume out of them unless you connect them to external speakers that need their own power supply to deliver the necessary current. Same is true if you decide on a string of programmable LEDs