Moving from Mambo to Joomla with housekeeping

[DirkDiggler]

I am running Mambo on a site which is intergrated with 8080 members, I want to move to joomla and SMF RC2 with a little house keeping. So I want to have a new database, but keep all the registered users and posts. I am curious as to which tables do I need to keep for the posts, PMs, Avatars, Catagories/Sections, and users. I just want to wipe out some backend errors I was having with some add-ons, you know start fresh. I eventually want to prune some old users and bogus emails, ill figure that out later. Any helpfull suggestions? Thanks guys.