A new transmission? If so what is approximate cost to replace or rebuild?

What is your question?

I have an automatic 2003 Pt cruiser. While driving it yesterday it started to jerk like it slipped gears about 3 times and then something popped. I coasted to a stop, engine was still running but won't move in drive or reverse. Checked transmission fluid it was fine. My step-father was able to get it to go just enough to get it loaded on his trailer to haul home. I dont know anything about cars so any help would be appreciated.