Export quicktimes as targa sequence with embedded alpha in HD

I'm receiving some HD Quicktime files tomorrow which I understand have an embedded alpha channel. I need to export them as targa image sequences, which I've never done in FCP before.

Will the alpha remain embedded in the targa sequence?
What TGA option do I choose (eg: million of colors, millions of colors+)?
Will I wind up with "high definition" targas? I understand HD Targas are just giant-sized images, is that right?

Anything else I should be aware of?

thanks