If I understand the problem correctly, it has to be a 50-50 chance. Three doors. Pick one. A door you didn't pick is opened, revealing a goat. Two doors remain, a car and a goat. You now get to switch or stay. How is that different than picking from two doors? Why would the original choice matter? And is a Lincoln Continental better than a goat?
Edit:
Nevermind, now I get it!