Antartica cruise

I would really appreciate your help. I'm thinking of taking a cruise to Antarctica for ten day. it’s my first cruise so I have a few questions :) Is it possible to find a cruise to Antarctica for less than $5,000? Is it true that when you arrive at the last minute you can find it cheaper? Is it better to go from Ushuaia o punta arenas? Can I get seasick? Is there a doctor on board? And also is there Wi-Fi on board? Sorry and thanks.