I wish to install a wordpress blog onto an existing site and integrate the design into the site.

The current site has a database that I'm using for a range of functions. Can this DB also be used for the wordpress blog or does that software require a dedicated/separate database?

Also can anyone point me in the direction of useful content about integrating the standard wordpress interface into an existing site. I guess something the addresses modifying default styles etc.

It would be great if anyone could help with this.

Appreciate any thoughts.