Hey stalefish,
to answer your first question....i am not aware if protein by itself increases metabolism, my guess is that it doesnt, but if you do not have at least 20g of protein for breakfast, you will have hyperglycemia (high insulin) for the whole day, that is why it is important to have protein at breakfast.
2nd question---protein should be a PART of a complete breakfast, so having a protein shake alone does not qualify...however if you are looking to lose some weight, a good substitute would be a meal replacement bar or drink.
Good luck,
Roman