Although I don't know of any good tutorials... I'm kinda playing with search engine stuff myself, and if you want to shoot me an email I'd be glad to bounce ideas back and forth...
postmaster@durdenwebapplications.com
You might check out this:
http://www.phpbuilder.com/columns/clay19990421.php3
I'm not sure I'd call that example too too advanced... the category bit of it should be easy to deal with if you're farmiliar with database stuff...
I woudl say your biggest issue might be actually getting the data... where is all teh data coming from and whos going to enter it all in :-)