Convert existing Site to CMS

This job is basically to convert an existing static art gallery site into a CMS based site. We don't mind Drupal, Joomla or Wordpress CMS. Whichever is cheaper to build in, but giving quality results. While most of the site structure will remain the same there will be some additions and changes to the existing structure. Please PM me if you would like to see the existing site URL. The owner of this art gallery is not very web savvy, so the CMS has to be as EASY as possible for him to use. For example, is it possible to have a strict structure on content pages that he cannot mess up, but can update? Could you quote in your PMs with and without strict structure. If not that is alright, I can just train him on using the normal CMS anyway, but would appreciate your comments and advice on this either way. There is also need for a search functionality and a Newsletter sign up (email input only) form, to database, on the homepage. The template structure will remain more or less the same as it is now, but I will do a redesign/re-skin of the front end. I will also create a new Flash movie for the home page to replace the existing one. PSDS and SWF will be provided. So integration of the Flash into the home page will be part of your side of the project. No linkage into the CMS is necessary from the Flash. Please pm me if you need any more info, and take a look at the site map file which has more information in it also. We require confidentiality, good communication, valid code and quality work.