How do you get an extract?

Extract in "vanilla extract" is simply the liquid extracted from the insides of a vanilla bean.

Extract means "to remove".

They're both flavorings, so as long as you don't mind the almond taste, why not?

Yes you can. Extracts or flavorings are interchangeable, according to your taste.

yes, as long as the flavor you want to achieve is vanilla and not maple.