Help !!! The butcher misunderstood me and gave me a pork shoulder instead of a pork leg. Can this still be made as a ham ??

Make this: https://www.bonappetit.com/recipe/braised-pork-shoulder-with-apple-cider-and-ginger-beer Along the same lines as your ham recipe, and a nice change from a standard pork shoulder. Happy Thanksgiving! ;o)

I would switch to the recipe for roast shoulder. The other recipe calls for a ham that has been cured already and since your should has not been cured, it will be a different process.

Fresh ham with apple cider glaze

Do you have the recipe you were planning on making? If it was a roast, you are good to go. If it involved curing the back pork leg, that's a longer process and trickier to adapt to the shoulder. Curing takes several days or weeks depending on what you are doing. A roast would just be cooked in the oven until the meat is done to your preference and a safe temperature. Go for the roast with your shoulder if you need it for tomorrow. Here's a good recipe!
https://food52.com/recipes/1747-cider-braised-pork-shoulder-with-caramelized-onion-and-apple-confit