alright, i am beginning to brainstorm ideas for a short film i will be making in april. this film will include several interviews, which i would like to set up like this:

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the green line would be an image (a logo on a black background) and the black circle would be the person being interviewed. my friend told me this would require chromakey, and if this is the case....

1) what will i need to do this? i would like to spend the smallest amount of money possible
2) would i be able to do this using sony vegas or the videomaking applications that come on apple laptops? if not, what additional software would i need? once again, i'd like to spend the least amount of money possible.
3) any tips or links to tutorials or anything like that? post them here!

thanks! if this is in the wrong place, please let me know