If you download the SEO URL's MOD
, you'll be well on your way there.
It has a few outstanding issues, but you'll at least be able to see 95% of what's needed to make it work.
If you understand the code a bit, you could modify it so that instead of having the topic or forum name in the URL, you could just use the forum or topic id's. (BTW, see the link for the SEO URL's MOD).