In his lectures, Plantinga argued that evolution and Christianity are not necessarily contradictory. Instead, it is natural philosophy that is antithetical to the Christian narrative of creation. Natural philosophy, or evolutionary naturalism, holds that there is nothing 'supernatural' because there is only the material world, nothing else exists.
His central argument was about how naturalism's statement of evolution actually undermines itself. Evolution, in Plantinga's logic, is an 'epistemic defeater' for naturalism. Naturalism holds that our basic tendency as developing animals is geared toward survival ('feeding, fleeing, fighting and reproducing'). Our human faculties are part of this development. If we really are surviving animals rather than believing or truth seeking animals, then, he argues, that those same faculties cannot be relied upon for any kind of truth claim, including naturalism or evolution. To believe in the reliability of our faculties would be a 'metaphysical add-on' to the evolutionary naturalism position. On the other hand, if we are creatures created by God (in God's image), even if by an evolutionary process, we would have warrant to trust our faculties with regard to belief in God and other broader truth claims (even those of science).
Since I am not a philosopher of religion, I will not explain this further, if I have really explained Plantinga's arguments with any clarity at all! I just wanted you to know that people of faith are thinking about these things, even if we intellectual peons do not really understand it all...