To make this ahead of time:
Stop after step 5 for the shrimp. Refrigerate the sauce in an airtight container for no more than 2 or 3 days. When you're ready to make the dish, re-heat the sauce to a simmer in a large pot then continue to step 6.
I do not recommend making the grits ahead of time. They take less than 10 minutes and the texture changes if they're left to sit. So I would make them while you reheat the sauce for the shrimp.