Filter not by category or tag but on custom taxonomy

Hello,

I have something like http://dribbble.com/shots/689969-New-Project/attachments/62603. That means that I have several filter parameter at the right side and would like to filter the postings by new attributes like level (beginner, advanced, ...).
1) Would you implement this new attribute as custom taxonomy and if yes how would I display the items that belong to this custom taxonomy?

2)What do I need to filter by several attributes like level + category + some other fields?

3) Is it possible to span the filter over several widgets (one widget for the category, one widget for the leve)? Or would you implement the filter as one widget?

4) How is it possible to drill-down and drill-up the filter attributes?

It would be great if someone could give me advice and maybe some keywords to get started with my research in the right direction.

thanks a lot, Sascha