Don't go crazy - there are newsletter templates right in word. To get to them - open word, then File, then Project Gallery - you will see on the left hand side a list of options choose - Newsletter - there are about 10 choices.
I have a mac also - your only other choice is Pages.
Our newsletter is created using Microsoft Publisher on a PC but I know that there are many samples in the File Exchange that are Microsoft Word files. If you have Office for Mac, you can open and edit any of the MS Word files and try them out. Good luck!