The brown stickers go on the grey blocks and the blue-grey stickers go on the blue blocks, right?Yes.
Are any of the sticker's 2-sided other than the leader? Or do I make 2 possible blocks for the leader, each with a single side?The Leader is SINGLE sided, so you get to choose whether you prefer heads or stripes. The leader is a hidden block just like the rest.
What do I do with the extra solid colored stickers and any extra blocks?Hang on for dear life, or variants, etc.
Would this principle apply to the other games?Yes.