If you are having contractions then you should go to labor and delivery or call the family birthing center.
Nothing. The mucus plug is not a big deal. If you are weeks away from deluvery, they regenerate. If you are close to your due date, wait it out. It could be tomorrow, it could be a while.
There's not really much to do. My one came out at 34 weeks and I'm now 37 :) if you feel fine don't worry about it