No, one of my friends completely changed her schedule in the middle of the sschool year just to change her elective about three times...... She went from Orchestra to Band to Choir, and she went from having all classes with me to only one, Math. So that's not too bad in my opinion.
No as you can talk to your teachers about which subjects and part of the schedule you want to change.It's better doing this early in the school year so you don't miss out on what's already been done in class.