Careful demo obviously I agree, but also I think that you should go into it with the idea that the mirror might not make it... be sure you're willing to replace it if it does break... or you might have a little heartbreak as well if the mirror does shatter.
Wow these are awesome tips. I was actually looking at vanities and they're SO expensive! I thought about constructing one myself from just a plain desk, but even those were more expensive than I thought. I'm definitely stealing your idea! I was also at HD this weekend and I saw the sign in front...