Style edit and portal page

Hi,

1. I would like to use PunBB forum on my website. I would like to modify a bit so it will match the style of my website. I know how to edit background img, colours ect. but can you help me find out which file I have to edit to add some div's for the header.
Basically I want to left the forum as it is but the background of the whole webiste where is the forum is diffrent and I would have to add header with navigation bar from my website.
Can you tell me what I have to edit to achive thi goal.

2. Is there any portal/front page for PunBB so I could use as a FAQ website with news ect...

Regards