Some people work by rote, so if the screen changes at all, they can't cope.
Others actually look at what is on the screen, and they will not notice that
this is not Excel; it just looks like a different version.

There are lots of free online tutorials, such as here:
http://www.baycongroup.com/excel2007/01_excel.htm

If you've ever used an adding machine, you should be able to use a spreadsheet,
with an hour of going through a tutorial. 90% of all spreadsheets use nothing
more than addition, subtraction, multiplication and division, along with sums.
You should be able to master that level of Excel in almost no time.