Well, I believe the message of the bible is true, not necessarily all of the details. If one believes in a literary Adam and Eve as archetypes of the human race, then saying that they sinned represents the fact that humans started to violate their consciences and thus sinned, but in a way that the ancients could relate to. There are different ways to look at Paul's view of Adam and not hold to an historic Adam, but I think the bottom line is that as long as the message is consistent, then the bible's authority and infallibility is upheld.
Again, if we hold the message of the scripture to the test of consistency and not every detail, then we know we can trust it.
No, I do not. I did for most of my Christian life, but it wasn't my accepting evolution that led to me changing my mind. For most of my evolution-believing life, I believed that Adam and Eve were the first 2 homo sapiens to evolve. It's learning about what paleontology, anthropology and population genetics teaches that led me to stop trying to concord early Genesis with history.