I have a MacBook Air and OpenOffice. I wrote documents from a PC using Word and sent it to myself by email.



When I downloaded the files and practice uploading them they were in an entirely different format

help

I don't know how Open Office has to be set up to read binary (Word 2003) .doc files. Otherwise, this might be relevant but probably not.
What happens when I send my document to someone else? Will Word mess up my formatting?

Word formatting is set by the active printer driver. I do not know if that is the case with Open Office.

You might have better luck asking this question on an Open Office or Office Libre forum.