I know how to generate a SAIL interface for a user's tasks for a running ins

Do you mean a running instance of a process model? In that case you can use numtasksforprocessmodelforstatus() to get the number of tasks with a specific status for a model, or getActiveTaskIDsForProcess() from the Task Smart Services Plug-in:
forum.appian.com/.../summary

I am referencing this: forum.appian.com/.../SAIL_Recipes.html --- I would like to display the Instance's Tasks in a grid as opposed to the User's Tasks.

Then you should still be able to use most of that tutorial, but just change the context for a!queryProcessAnalytics(). Replace the report you created for a specific user with the OOTB report "Tasks per Process Model".

With this you will also need to use the "contextProcessModels" field of a!queryProcessAnalytics() to pass in the desired process model as a context for the Tasks per Process Model report