First I'd like to say that everything we believe from the Bible is important, but of course some things are more important than others. Second, everything in the Bible has truth attached to it, and since there can only be one truth how we interpret such truth becomes critical to our present well being and eternity.
With that as my foundation I can strongly assert that when discussing the Bible (a book given to us by God for instruction) that consists of 66 separate books written over a long period of time and many different authors it is absolutely critical how we interpret it. Then considering that the first book discusses our origins and the root of all the problems we in the world are experiencing today; yes I think it is extremely important how we interpret it. Don't you?
Imagine taking any modern well known book of instruction that in the first chapter outlines the history of how the author came to tell you his reasons for writing the book. Then imagine misinterpreting the meaning of that foundational first chapter, obviously the rest of book will, to at least some degree, be less meaningful and thereby easier to misinterpret. Given the life and death ramifications that the Bible teaches you will have to multiply the degree of consequences by a lot to even remotely compare it to something else. I hope you can begin to see the importance that the book of Genesis has and the effect it will have on our soul for eternity. If we misinterpret those foundational truths, how much more likely are we to do so with the rest of the Bible?
There are plenty of combative things I could say here - and if that was all I had to say I just wouldn't reply. However I'm curious about something. How does this statement that "Genesis is foundational" actually work out in practice?
I'm asking because when I deal with new Christians / spiritual seekers, I don't usually direct them to Genesis. Obviously my bent in origins theology has something to do with it

but I have other reasons as well, and I was just wondering if you could comment on them.
For one, most people who start with Genesis continue with Exodus, and then plan to continue with Leviticus and never do. Thus they never get around to Luke, let alone Romans or Ephesians. I have an agnostic seeking friend who's gotten trapped right there, and I think you'll agree that this isn't a helpful way to (not) read the Bible!
For another, I don't see Genesis making sense to someone with little knowledge of the Gospel. Ok, so God makes everything in six days and finishes with man. (And then he makes man
before animals in Chapter 2, depending on your translation. That aside.) Then in Chapter 3, there's a snake - whoa, where did he show up from? And ok, so they ate a fruit God didn't want them to, but isn't God being a bit harsh to everyone involved? I mean sure He promised them that they would die, but He didn't say anything about painful childbirth! Or working for food! Or this curse on the rest of creation that you guys keep talking about! And on it goes ... I don't know about you, but when I see someone with little to no understanding of the Christian faith, I find it a lot more helpful to direct them either to Luke and John (if they absorb more narrative) or to Romans and Ephesians (if they're more intellectual). What do you think?
I agree with you that someone who gets Genesis wrong will have a diminished view of the rest of the Bible, but I think that's true just in the sense that every book in the Bible depends on every other book, and that Genesis isn't special in that regard. (Is the page of contents infallible?

) I'm saying that not just as a Christian who accepts evolution, but as someone who in guiding new believers often finds it a lot more helpful to point them to Jesus and the Cross first and foremost.