The above advice is right on. Recently, I had an opportunity to buy a slightly used road bike from a friend. Even though we are built almost identical, I didn't trust it. (I had been reading the posts on TE for a while and learned a thing or two.) Since it's an REI bike, I went to my closest store and had them fit me. Luckily, it turned out, her bike was my fit. Now she's mine and with a little adjustment here and there we are very happy together. There are still some minor things I want to change, like the seat and raising the handlebar stem, but the overall frame dimensions are good. The rest can be worked with.
Good luck.
-X.