Select the part that has the upside down face, At the top left click on polygon modeling, in a menu that pops up hit convert to poly or apply edit poly mod, then go to your tool bar to the right and hit modify. From there look down and under selection click face. go to the parts that need to be fixed and select them by holding ctrl and clicking on them, once all are selected go back to your tool bar on the right and scroll down till you see flip, then click and your done.