For fresh sour cherries, you will need to wash them, pitt them, and then add 2 cups of cherries to 1 cup of sugar. Bring to boil until the cherries are juicy and tender. Taste for sweetness, realizing that sour cherries live up to their name and will never sweeten completely. Add vanilla when you take them off the heat, about 1 tsp per 2 cups of fruit. Also, to thicken the juice, add 1 tblsp of cornstarch that has been blended with about 2 tbslp of water until it makes a medium thin paste. Stir carefully into your juicy fruit before adding it to the pie shell. I would then dot the top of the fruit with dabs of butter, and sprinkle in cinnamon and sugar. On the top of the crust repeat the butter bits, and cinnamon and sugar so it browns nicely with a sweet crust.
Good luck, remember, it will be a bit tart, but that's ok!