explorador - 5:37 pm on Apr 29, 2013 (gmt 0)
+1, now that your site already made it to the search engines and surely into other people pages (links) it's important to keep your url structure.
As for SEO effects well it depends. In my experience even keeping my complete url structure I had mixed results. IMHO keep the html as clean as possible, fast, simple, lightweight and you'll be fine. Usually cms can add unnecessary code. Ohhh and you mentioned Keywords... well, some CMS allow you to use keywords and meta tags, others won't. I mean, it's not so easy to replicate your present html with a cms but yes, it is possible. Give it a try and keep your backup just in case.