The opponent changed formation? Having seen the teams, I would say your formation does not matter too much. Pick any players you want, maybe your youngest players to get the most development, and then play them in a legal formation attacking down the wings. 4-5-1V or something similar would be good.
I don't know how many teams you're asking me to plan against for you since the original question was 4-3-1-2, but I stick to what I said. As long as you have a legal formation, everyone in position and in good condition, you should win comfortably. I'm not sure how you managed to draw the first leg. :s