I just got my great grandfather's straight edge from my grandmother as a gift and I really would love to learn how to use it. I've read this site and what I've learned is that I know nowhere near enough to do anything.

How do I sharpen it? (because it is about as sharp as my pocket knive)
Should I buy a new one and get used to shaving with it before I try to fix my g grandfathers blade?
How would I go about choosing a good blade and not getting jipped?
please help