Upgrading Current Site to WordPress with no Downtime?

[GheP]

Currently, my father built a website for his business in Photoshop and used a SiteGrinder plugin to create the website. We are very unhappy with the look and feel and want to switch it over to WordPress. I have a blog in WordPress, so the installation and use of WP isn't an issue.

I am having trouble finding the best solution to go about this with ZERO downtime because it's for his business.

I thought about putting all of the folders/images into another directory and having the index.html redirect to this newly created directory - at the same time, installing WordPress and developing the theme/look/feel in the root directory. Only problem I see, is the links/pages being incorrect because of the directory change.

Can anyone help me? We would like to keep this all within one domain.

[Fang]

http://codex.wordpress.org/Moving_WordPress

[GheP]

Thank you Fang, but I don't think that completely answers my question.

Are you suggesting I install WordPress in a separate directory and leave the current site up, install all my themes, widgets and plugins in WP, then move WP into the root directory?

[Fang]

Are you suggesting I install WordPress in a separate directory and leave the current site up, install all my themes, widgets and plugins in WP, then move WP into the root directory?

Yes

[GheP]

Does anyone (including Fang) know of any other alternatives to what Fang suggests?

Second opinions never hurt :P

To clarify, since I cannot edit my initial post: When I said:

I have a blog in WordPress, so the installation and use of WP isn't an issue.

I meant that, I have experience in installing WordPress for a separate and previous (personal) blog.