Iweb to Wordpress - web designer help please!

Hi there all,

I've trawled the web and dpreview for help on this to no avail. I've posted on facebook, even emailed the producers of the wordpress theme I want to use. No idea how to approach this issue, so I turn to the trusty forum.

I built http://www.thomasstewart.com.au using iWeb. I'm pretty happy with it. But, things are going well, I'm getting lots of traffic and business, and I'd like to move to a more professional hosting system. I'd want to re-build my entire site in wordpress (hosted on my own domain), using a pro theme (Photocrati). I guess it'd be a blog-site.

Just to clarify, this isn't just a blog migration; I want to delete my iweb site, upload and install WP and a theme, and re-build the entire site on my main domain (not a subdomain). My blog is currently hosted by wordpress and will be easy to import.

The problem? I'm ranking very well in google for various key words that I've chosen. I've used iWeb SEO tool exhaustively and am happy with my SEO. I don't want to destroy all my hard work by just deleting my iWeb pages, installing WP, and waiting for those new pages to achieve positive google rank.

So. How do I do this? What would happen if I left my iWeb pages live, changed the content to say 'site has moved', so that I still benefit from those pages' google rank, while also installing WP and running that from the server too? Could I just rename the wordpress pages with the same .html names as the old iWeb ones, thereby maintaining the link between the search result and a page?

Does this even make sense?? Sorry for being confusing. I'd really really love and appreciate any help and advice. Not sure where else to go on this issue.

Thank you in advance