Wow Karen, those are some questions!
Yes you have to go back to where you landed in your spacecraft and tip it over the edge. Be sure that you have that metal rod with you in inventory. You will have to move it before you will be able to leave the moon.
No you do not have to do any of the gear puzzles to get back inside but you may possibly have to do the gate to the Necropolis again before you will be able to leave. One of the requirements will be to return things you took from the sarcophagus.
You don't have to shatter the bust, you can get salt elsewhere in the game just as easily.