I am trying to create a formula that will tell me how many days a task was open whether or not its status is complete. In other words, if the project is complete it should calculate total days it was open and if its still in progress it should return number of days based on todays date.
You could probably do this with a form rule and a formula duration field. Basically the form rule would update a date field when the status changes called Date of Status or something. Then in your formula field you can either compare that date to today or the date of status to today.
If status is complete then it should get number of days between the date is created to the date it was marked as completed otherwise it should show the number of days since the date it was created to today.