I wouldn't recommend your approach. I've done what you are trying to do, several times, with great success. But using the approach of building WordPress in a well-named directory, say /wp/ or something like that.
Once my site is ready to go live, I simply renamed (my old HTML site's) index.html in the root to something like oldindex.html, copied (NOT moved) index.php from the /wp/ directory to the root, changed this copy of index.php to point to /wp/, changed the Site URL in WordPress Settings to point to the root, and did a Save on Permalinks to make all the links appear to the visitor as being the root.
The full details on doing that are here:
http://codex.wordpress.org/Giving_WordPress_Its_Own_Directory#Using_a_pre-existing_subdirectory_install
Manually moving WordPress is a recipe for disaster in my experience.