Replaceing Vb logo with a banner

[kalliusss]

Heya there folks!

I understand you guys probaly get asked this constantly but none of the posts I have read are very clear to understand, I'm a new Vb user so I'm a little clueless to even the basics right now.
What I'm trying to achieve is i'd like to replace the Vbulletin logo with my own banner but I want the banner to stretch from left to right if you get me, covering the entire area you see left open with the default logo in place. I understand well atleast I think it has something to do with makeing the site fixed which I'm not sure how to do. Another quick question is would I be able to add a banner below the navbar but above the content, I would love to have a tab saying Join Us with a banner acting as a link to an application form.

I dont mean to annoy anyone by asking these questions. I havnt touched anything to do with these on my site as I don't want anyone going to the trouble of helping me then for it not to work because of something I messed up.

EDIT: I have just found a site with the same layout I have in mind the URL is http://www.sanctuary-guild.net. That's the position of the banner I would like and they also have the join us tab I was thinking of.

Thanks in advance!!