Premium Unlimited & Int'l Service Capability in France, Italy & Switzerland

If I switch my plan to Premium Unlimited trip to France, Italy & Switzerland, will I have access to international calls, texting, and data included in the Premium Unlimited plan at no additional charge. I understand that for me, switching from Unlimited to Premium Unlimited will be $10/month more per line. Also, will I be able to switch back easily upon my return to the United States?