It's good to get paranoid around the web these days. Another thing to get paranoid about is being ready before the launch. I mean really ready. I've seen people invest a lot of money in mail shots and promotion for a launch, but not be ready when they should have been. Bang goes the promortion, and worse, all the media and suchlike that try to hit your site when it's down are left with a totally negative impression.
It is better to delay the promotion for a fortnight than have that happen. So, make sure it is ready then wait a fortnight and make sure it is still ready before you start promoting it. Get everyone you know to test the new site out, get them to hammer it and see what happens.
As to securing files and stuff from prying eyes, spend some time reading up on all the lovely things you can do with .htaccess , and implement all the security you can.