[Typo3] Newbie question for a complex site

[Alan Langford]

Hello everyone. I've been working with Typo3 for a week or two now and I 
really like it. I've gone through the tutorials and every document that 
looks relevant, but there's some basic questions that I can't get my 
head around.

Most of my trouble comes, I think, from too much experience with CM 
systems that are driven off HTML templates. Typo3's approach is clearly 
better, but the transition is a little confusing.

I'm working on porting a site with a fairly complicated design that's 
currently generated with custom PHP and no content database. The site 
has several main sections. All of the sections have many elements in 
common, and some elements that are different (for example the background 
colour in the main content table cell). The layout is sufficiently 
tricky that I have tables nested three deep by the time I get to 
rendering content.

I'm thinking of putting a ###SECTION_CSS### tag in the HTML template and 
using that to insert the appropriate styles for each section. Is that 
the best approach?

Layout: The PHP code is set up so that I can change constants for the 
size of the site main logo and then all the fixed table sizes are 
adjusted automatically. This makes it really easy to adapt when the 
client decides the logo is too big on Monday and then too small on 
Thursday. Can someone help me understand how to do this in Typo3?

Navigation: There's a horizontal menu across the top of the content with 
a link for each section. Then there's a menu on the left hand side with 
the page tree within that section. I'm not sure how to organize the site 
to get both menus running automatically. Should I make each section a 
"site" or is there a way to say "create a menu from this point in the 
page tree down"?

Thanks in advance for any assistance!