To be honest, the solution I almost always opt for is the .htaccess 301 redirect and there is a great tutorial on .htaccess files here: http://blog.dreamhosters.com/kbase/index.cgi?area=3083
The only URL you’ll need to redirect is the top level one (the blog main page), all other links will eventually die out, but the new links from the index.php will propagate nicely with the html file out of the way.
You need to check if your server has an .htaccess file. If so, open it and add one or both of the following lines (depends on how your server is set up). Be careful with the second line as if could cause you to go into an infinite loop. I suspect only the first line is needed.
Now of course you are going to have to fill in all the appropriate paths so it’s best you backup anything before starting, that way you can always go back and try again.
DirectoryIndex index.php
Redirect 301 /index.html http://www.yourdomain.com/index.php