Custom menu L2 landing pages

Hi

I am building an information site with WordPress, so there are alot of content pages in a hierarchy of 4 levels.

I would like my Level 2 landing pages to act as menu pages for Level 3: A page containing an html table-grid which displays the menu output as a gallery with short description of each item.

So for example from the home page, if a user clicks on “Fruit”, they would be taken to a Level 2 landing page displaying the fruit custom menu, output in a grid with thumbnail images and a short description of each.

Thanks for choosing to read about fruit. You can find out lots more about different fruit if you click on the pictures below.

[Lemon image & desc] [Oranges image & desc] [Peaches image & desc]

etc.

However, if on the home page, the user clicks on “Animals”, they would be taken to a Level 2 landing page displaying the animal custom menu.

I’m thinking CSS styled custom menus would be the way to approach this, rather than creating each menu landing page manually.

So my questions are:
1) My template only allows one header menu at the moment, so I think I have to do something to initiate custom menus.
2) How do I add a custom menu to a template?
3) How do I show different custom menus depending on site section?
4) How can I define an image and description for each custom menu item?

Thanks