How to modify default skin?

[pein87]

i`d like to modify the skin but I dont know to much about xml and how the skins are coded. What i`m trying to do is add a 300 pixel picture to the top and replace the vbulletin logo with my own graphic. I`d lke for it to be as long as the main table. I`d alos like to make a another image on the forums bottom thats 150 pixels. I`m sure its a table but I dont know where to put it in the header and footer templates. I own an anime site and I`d like to have a nice graphic on both top and bottom that spans the borads lenght. I`m also using 805 on the mina table so Its easier to view the forums. Also how do i change the background color of the mina table and of the body of the document so the there to my liking? If anyone can help i`d really appreciate it.