Hi! I am trying to use Microsoft Word and type in
Sanskrit and Tibetan...
Sorry, MS Word for Mac is still unsuitable for such a task, it cannot yet do Devanagari/Sanskrit, Tibetan, Arabic, or Hebrew. (It can probably do transliterated Sanskrit, however).
You will need to use a different app, many of which can save in .doc format if necessary.
Devanagari or transliterated Sanskrit can be done with OS X as it is (except for stress marks I think). This note indicates some suitable apps, to which should be added OpenOffice/X11:
http://homepage.mac.com/thgewecke/TypingDevanagari.html
Here is a page on Sanskrit:
http://homepage.mac.com/thgewecke/sanskrittest.html
Tibetan requires the Xenotypetech kit. Or you can do it with OpenOffice/X11 plus a downloadable keyboard and fonts.
Leopard when it comes out next spring should include Tibetan.
Feel free to ask or email if you have further questions.