Using the wp-functions in a custom website

Hi folks.
I take care of my band’s website (www.cnomania.it), which I built 2ys ago. Now I would like to integrate wordpress into the website to manage the news, links and gigs (through an event plugin I am developing); I have seen a couple of tutorials, but they are not really about what I want to do, for they build a brand new wp theme that mimic the website theme. I would like to use the wp engine without the themes; I would like to modify my website code only to introduce the wp-loop and template tags instead of my interrogations to my database.
Which is the best way to accoplish this? I had though of putting wordpress in the http://www.cnomania.it/wordpress subdirectory, but I would like my home to remain http://www.cnomania.it/index.php.
I am sure I need to modify my website headers to include some call to the wordpress engine bu I don’t know where to start from.
Any suggestion?