I came up with a set of rewrite rules that pretty much covers my site.
RewriteEngine On
RewriteRule ^([0-9]+)/([a-zA-Z0-9-]+)\.html$ /index.php?id=$1&title=$2 [L,nc]
RewriteRule ^([0-9]+)/([0-9]+)/([A-Za-z0-9-]+)\.html$ /index.php?id=$1&mo=$2&title=$3 [L,nc]
RewriteRule ^([0-9]+)/([0-9]+)/([0-9]+)/([A-Za-z0-9-]+)\.html$ /index.php?id=$1&mo=$2&exp=$3&title=$4 [L,nc]
It turns out most of the work was required on the web pages themselves. Restructuring all the internal links, to look more SEO friendly. The need for lots of absolute URL's instead of relative ones was a bit of a pain. But I think I have most of those corrected now.
Add some PHP entry code to rewrite the main entry page, which has specific content.
More code to have dynamic page titles. That was a nice addition.