"OK, would someone mind explaiing how to graph two textures together, so that only part of one shows through the other. I learned a lot from Mike's site, but it didn't really show me HOW to make one."

You'll need to use a layered texture. Look in the docs under Shading>About>Materials In Maya>Layered Shaders. I recommend you use a layered texture, NOT a layered shader. You'll have much more control.

"Also what is the best way to use a transparency mask on a simple cube, so that it renders in the shape of a leaf by masking the edges of the poly???? I am lost in these 2 areas."

Simply assign an alpha channel, or a B&W texture to the transparancy channel of your shader. However, it's won't look solid. You will see the front and back side of your cube. The only way to fix that would be to model the leaf, or to come up with a displacement technique to make the edges come together.