dynamic mask, animated sprites and dual movie clip textures...

Hi I'm new to Unity and am working on a basic game in the pro version,
I have a few graphic questions relating to the games GUI.
If anyone has a minute to spare I'd really appreciate some feedback.

1. When the player collects objects I want an animated bubble to appear with a number on it and float upwards and then disappear. Is the easiest way to do this either:
A) After FX using an animated png sequence
B) Flash using a 3rd party flash swf importer
C) Using a sprite generator within Unity
D) Using a psd file with a pre-made script

2. I'd like to have a dynamic mask which controls the visibility of a powerbar (the mask would start at 100% height and gradually decrease in height unless objects are collected).....what is the best way to do this ?

3. I want to swap seamlessly between 2 movie clips - these clips would be applied to a 2d surface. Am I right in thinking that I would have two surfaces in the exact same position with different movie textures applied to each and that I swap between the visibility of each surface. Is this the most efficient way of doing this and if so is there an example unity file anywhere ? Is there a button

Thanks
Joey