Prep time does not include time to cook the pumpkins. That step can be done right before making the pie, or any time up to 6 months in advance, if the puree is frozen. This is a combination and modification of recipes from my step-mother and 'Healthy Meals in Minutes'. The recipe calls for fresh-cooked (or frozen) pumpkin puree, which really is best, but you can substitute canned pumpkin if you are pressed for time. I like the squashed-looking 'Cinderella' pumpkins best for cooking with - the kind used for carving really aren't very good to cook with, unfortunately. I bake one or two every Fall and freeze the puree to use in recipes for the rest of the year. I find pumpkin pies made with fresh, rather than canned, pumpkin have a more delicate flavor and smoother texture. Try it! I have used the same amount of all kinds of milk - 1%, 2% whole, whipping cream, evaporated, sweetened condensed - and have also substituted up to 1/2 the amount of pumpkin puree with squash or sweet potato puree and can't tell the difference in the final product.