Best way to move a site onto WP?

I have an existing site that is built on Joomla and I will be moving it over the WP soon. My plan, to preserve links, traffic, etc., is to create a sub folder and move the entire Joomla site into it. I then want to put in 301’s to redirect domain.com/post.html to domain.com/archive/post.html so anyone coming to the site from a previous link or bookmark will go to the original content while I recreate all those posts in WP. I’ll then replace those 301’s with new 301’s that redirect the old posts to the new posts, and delete the archive folder and the Joomla site with it.

So, my question is, will it work? Will the current site still be able to access the mysql for the posts? Will the plugins and images fail because they don’t have the right path? Any other suggestions on the best way to move a site over?