If you want to be prepared, do the following things.
1. Learn shortcuts
2. Learn xmldata import/export
3. Learn pivot tables
4. Learn formulaes
5. Install 2007 office suite, and go thru the tooltip when you enter a "=" in any cell.
6. Try creating and running macros. Put your wildest thoughts and make them as requirements and frame a macro.
And as parttime- look at eggheadcafe Microsoft Excel..section..there are quite a handful of people who post challenging problems. try to solve them.
I am sure you would be prepared for the assault.