Excel 2007 : Installing Excel (Office Home and Student 2007) over Office 2000

Hi

I have just bought Office Home and Student 2007 which I intend to install, but have not yet done so, over Office 2000 (Excel, Word and Powerpoint).
At present I use a simple, small program to deal with church finances, using three worksheets which automatically update each other and I am about half way through the year. What I would like to know is:-
1. Using 2007, will I still be able to update or change the old figures ?
2. Will Ron de Bruin's excellent program "Send Mail" still work ?
3. Any other issues I should be aware of ?

Thanks

David H