Categories and subcategories on page, not sidebar

I'm going to have a million questions while moving from asp/html to MU!

I'm looking at Marketpress and Woocommerce, and Custompress; with lots of questions.

The site I'm moving has 40 categories with about 1600 subcategories (total, not each!).

I need to list the categories in a page - in the content area, not in the sidebar - and have each one link to another page (or post, whichever) that lists the subcategories for the clicked on category.

From there, clicking on a subcategory would take you to something like a search results page that would show a thumbnail of the product on the left, a short description next to it, plus some custom field content next to that, with about 10-15 per page.

Clicking on one of these would take you to the full product page.

Where do I start? How can I put the categories on a page, rather than in a widget in the sidebar?

Also, I need a page that lists all the categories and their subcats in a long list, where again the links go to the search results-like pages for each cat/sub. But in the content area, not in the sidebar.

Thanks for any ideas!