How to move WP (in "/blog" )back to the root folder ?

Hi
i use wp on my site for 2 years now. it is install in a folder named “/blog”
now i am thinking moving all my site content into wordpress, so i think it would be good to move it down to the Root folder of my site.

question : how to do this the good way ??

don’t want to miss things up with SEO, my page archived into Google, getting 404 errors, etc… how to avoid this ?

example of present links :
http://www.mysite.com/ = custom php/html homepage (non WP)
http://www.mysite.com/blog/ = index page of my WP
http://www.mysite.com/blog/2010/title-xyz = singlepage link inside WP (with date auto-added in front)

i got 7 categories. One is named the same as the WP folder, which means it’s named “/blog/category/blog”