You would perhaps be happier using Works instead of Word.

In Word, imported documents are usually a mess as far as formatting goes. They may look fine but trying to make changes can be a real headache.

To answer your direct question: to remove all direct formatting from Word:
Ctrl+A to select all
Ctrl+Q to remove paragraph level formatting
Ctrl+Spacebar to remove font-level formatting

I would be surprised if this gives you the result you want, though.

If you are going to continue using Word, I would recommend doing a bit of study. You will be much happier and more efficient. Trying to use Word without using its tools is like trying to push a rope. It fights back and gets tangled.

Basic concepts of Microsoft Word: An introduction